Cloning and characterization of a gene (RNF22) encoding a novel brain expressed ring finger protein (BERP) that maps to human chromosome 11p15.5

EF1α-associated protein complexes affect dendritic spine plasticity by regulating microglial phagocytosis in Fmr1 knock-out mice

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. There is no specific treatment for FXS due to the lack of therapeutic targets. We report here that Elongation Factor 1α (EF1α) forms a complex with two other proteins: Tripartite motif-containing protein 3 (TRIM3) and Murine double minute (Mdm2). Both EF1α-Mdm2 and EF1α-TRIM3 protein complexes are increased in the brain of Fmr1 knockout mice as a result of FMRP deficiency, which releases the normal translational suppression of EF1α mRNA and increases EF1α protein levels. Increased EF1α-Mdm2 complex decreases PSD-95 ubiquitination (Ub-PSD-95) and Ub-PSD-95-C1q interaction. The elevated level of TRIM3-EF1α complex is associated with decreased TRIM3-Complement Component 3 (C3) complex that inhibits the activation of C3. Both protein complexes thereby contribute to a reduction in microglia-mediated phagocytosis and dendritic spine pruning. Finally, we created a peptide that disrupts both protein complexes and restores dendritic spine plasticity and behavioural deficits in Fmr1 knockout mice. The EF1α-Mdm2 and EF1α-TRIM3 complexes could thus be new therapeutic targets for FXS.

Overexpression of ST7-AS1 Enhances Apoptosis and Inhibits Proliferation of Papillary Thyroid Carcinoma Cells Via microRNA-181b-5p-Dependent Inhibition Tripartite Motif Containing 3

Long non-coding RNAs (lncRNAs) are of great significance in the pathogenesis and progression of papillary thyroid carcinoma (PTC). LncRNA tumorigenicity 7 antisense RNA 1 (ST7-AS1) is a newly identified lncRNA serving as an oncogene or tumor suppressor in different tumors; however, the role of ST7-AS1 in PTC remains completely unknown. In this study, ST7-AS1 was mainly distributed in the cytoplasm of PTC cells and presented reduced expression in THCA tumors and PTC cell lines. Functional experiments revealed that overexpressed ST7-AS1 inhibited the viability and proliferation of PTC cells, whereas accelerated the apoptosis of PTC cells. The expression of miR-181b-5p was upregulated and it bound with ST7-AS1 in PTC cells. Moreover, TRIM3 exhibited downregulated expression level in PTC cells and ST7-AS1 elevated TRIM3 expression via harboring miR-181b-5p. Rescue experiments illuminated that knockdown of TRIM3 reversed ST7-AS1 overexpression-induced promotion on PTC cell proliferation and suppression on PTC cell apoptosis. Overall, overexpression of ST7-AS1 enhances apoptosis and represses proliferation of PTC cells via targeting the miR-181b-5p/TRIM3 axis, which may help broaden the horizon and establish the foundation to develop therapeutic strategies for PTC in the future.

Circular RNA circVPRBP serves as a microRNA-106b-5p sponge to regulate proliferation and metastasis of cervical cancer cells via tripartite motif-containing protein 3

Cervical cancer is a common malignant gynecological tumor for females all over the world. Circular RNAs (circRNAs) are being found to have relevance to various human cancers, including cervical cancer. This study is designed to explore the role and mechanism of circRNA DDB1- and CUL4-associated factor 1 (circVPRBP, also known as hsa_circ_0065898) on the progression of cervical cancer. CircVPRBP, microRNA-106b-5p (miR-106b-5p), and tripartite motif-containing protein 3 (TRIM3) levels were determined by real-time quantitative PCR. Cell proliferative ability, apoptosis rate, cell cycle progression, migration, and invasion were detected by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide, 5-ethynyl-2'-deoxyuridine, colony formation assay, flow cytometry, and transwell assays. Protein levels of matrix metallopeptidase 2 (MMP2) and matrix MMP9, and TRIM3 were measured by western blot assay. The binding relationship between miR-106b-5p and circVPRBP or TRIM3 was predicted by Starbase and then verified by a dual-luciferase reporter and RNA immunoprecipitation assays. The biological role of circVPRBP on cervical tumor growth was examined by the xenograft tumor model in vivo. CircVPRBP and TRIM3 were decreased, and miR-106b-5p was increased in cervical cancer tissues and cell lines. Furthermore, circVPRBP could suppress cell growth and metastasis of cervical cancer cells in vitro. Mechanically, circVPRBP could regulate TRIM3 expression by sponging miR-106b-5p. Also, circVPRBP upregulation repressed tumor growth of cervical cancer cells in vivo. CircVPRBP could inhibit the malignant biological behavior of cervical cancer cells by miR-106b-5p/TRIM3 axis, providing a promising therapeutic target for cervical cancer treatment.

Research progress on exosomal proteins as diagnostic markers of gastric cancer (review article)

Gastric cancer (GC) is one of the most common types of tumors and the most common cause of cancer mortality worldwide. The diagnosis of GC is critical to its prevention and treatment. Available tumor markers are the crucial step for GC diagnosis. Recent studies have shown that proteins in exosomes are potential diagnostic and prognostic markers for GC. Exosomes, secreted by cells, are cup-shaped with a diameter of 30–150 nm under the electron microscope. They are also surrounded by lipid bilayers and are widely found in various body fluids. Exosomes contain proteins, lipids and nucleic acid. The examination of exosomal proteins has the advantages of quickness, easy sampling, and low pain and cost, as compared with the routine inspection method of GC, which may lead to marked developments in GC diagnosis. This article summarized the exosomal proteins with a diagnostic and prognostic potential in GC, as well as exosomal proteins involved in GC progression.

Tripartite Motif Containing 3 inhibits the aggressive behaviors of papillary thyroid carcinoma and indicates lower recurrence risk

BACKGROUND

Tripartite Motif Containing 3 (TRIM3) has been reported to be downregulated in several malignancies. However, its prognostic significance in thyroid cancer remains unknown.

OBJECTIVE

Here we aimed to investigate TRIM3's expression and its involvement in papillary thyroid carcinoma (PTC).

METHODS

Clinicopathological analyses were performed in patients with PTC. Expression of TRIM3 protein was evaluated by IHC. The prognostic role of TRIM3 in PTC patients was assessed by univariate and multivariate analyses. Cell proliferation and invasion were tested in two PTC cell lines following overexpression or knockdown.

RESULTS

TRIM3 was decreased in PTC tissues compared to adjacent thyroid tissues on both mRNA and protein levels. Additionally, low expression of TRIM3 was significantly related to tumor size, lymph node metastasis and TNM stage. Moreover, TRIM3 was identified as an independent prognosis factor by multivariate analysis. Cellular data revealed that TRIM3 can inhibit the proliferation and invasion of PTC cells. Consistently, TRIM3 can upregulate the expression level of E-cadherin, while downregulate N-cadherin, Vimentin, and cyclin D1 expression.

CONCLUSIONS

TRIM3 expression was downregulated in PTC tissues comparing with that in adjacent nontumorous thyroid tissues. Lower TRIM3 expression in PTC can contribute independently to a poorer prognosis by enhancing PTC proliferation and invasion, highlighting its potential as a novel therapeutic target and prognostic biomarker.

Tripartite motif-containing 3 (TRIM3) enhances ER signaling and confers tamoxifen resistance in breast cancer

Tamoxifen resistance remains a clinical problem in estrogen receptor (ER)-positive breast cancer. SUMOylation of ERα enhances ERα-induced transcription activity. Tripartite motif-containing (TRIM) proteins are a new class of SUMO E3 ligases, which regulate the SUMOylation of proteins. However, the precise molecular mechanism and function of TRIM3 in SUMOylation and the response to tamoxifen remain unclear. In the present study, we observed that TRIM3 was dramatically overexpressed in breast cancer, which correlated with tamoxifen resistance. Furthermore, TRIM3 overexpression significantly correlated with poor survival of patients with ER⁺ breast cancer treated with tamoxifen. TRIM3 overexpression conferred cell survival and tumorigenesis, whereas knocking down of TRIM3 reduced these capabilities. Moreover, TRIM3, as a ubiquitin carrier protein 9 (UBC9) binding protein, promoted SUMO modification of estrogen receptor 1 (ESR1) and activated the ER pathway. Silencing UBC9 abolished the function of TRIM3 in regulating tamoxifen resistance. These results suggest TRIM3 as a novel biomarker for breast cancer therapy, indicating that inhibiting TRIM3 combined with tamoxifen might provide a potential treatment for breast cancer.

Tripartite motif-containing 3 (TRIM3) inhibits tumor growth and metastasis of liver cancer

BACKGROUND

Reduced expression of tripartite motif-containing 3 (TRIM3) has been reported to be involved in the pathogenesis of human glioblastoma. In our previous research, we found that TRIM3 expression was markedly reduced in human primary hepatocellular carcinoma (HCC) tissues and that low TRIM3 expression was associated with short survival of HCC patients. However, the role of TRIM3 in liver cancer remains unknown. This study aimed to investigate the function of TRIM3 in liver cancer cells.

METHODS

The protein levels of TRIM3 in five liver cancer cell lines (SK-Hep1, Hep3B, Huh7, HepG2, Bel-7402) and one normal liver cell line (L02) were detected with Western blotting. HepG2 and Bel-7402 cells with low TRIM3 expression were infected with recombinant lentiviruses overexpressing TRIM3 (LV-TRIM3), whereas Huh7 and Hep3B cells with high TRIM3 expression were transfected with TRIM3-targeted small interfering RNA (siTRIM3). The functions of TRIM3 in the proliferation, colony formation, cell cycle, migration, invasion, and apoptosis of the above cell lines were examined. The effect of TRIM3 on tumor growth and metastases in nude mice was also investigated.

RESULTS

TRIM3 was overexpressed in HepG2 and Bel-7402 cells with LV-TRIM3 infection, which further reduced proliferation, colony formation, migration, and invasion of both cell lines. Cell cycle analysis showed that TRIM3 overexpression induced G₀/G₁ phase arrest in HepG2 and Bel-7402 cells. Moreover, apoptosis was not increased in HepG2 or Bel-7402 cells overexpressing TRIM3. Contrarily, silencing TRIM3 expression in Huh7 and Hep3B cells by siTRIM3 led to significantly decreased percentages of both cells in the G₀/G₁ phase and promoted cell proliferation, colony formation, migration, and invasion. In vivo experiment results confirmed that TRIM3 overexpression suppressed tumor growth and metastasis.

CONCLUSIONS

TRIM3 plays a tumor-suppressing role in the regulation of liver cancer development by reducing cell proliferation through cell cycle arrest at the G₀/G₁ phase.

TRIM-NHL proteins in development and disease

TRIM-NHL proteins are key regulators of developmental transitions, for example promoting differentiation, while inhibiting cell growth and proliferation, in stem and progenitor cells. Abnormalities in these proteins have been also associated with human diseases, particularly affecting muscular and neuronal functions, making them potential targets for therapeutic intervention. The purpose of this review is to provide a systematic and comprehensive summary on the most studied TRIM-NHL proteins, highlighting examples where connections were established between structural features, molecular functions and biological outcomes.

Advances and challenges in the molecular biology and treatment of glioblastoma-is there any hope for the future?

Malignant gliomas, such as glioblastoma multiforme (GBM), present some of the greatest challenges in the management of cancer patients worldwide. Even with aggressive surgical resections and recent advances in radiotherapy and chemotherapy, the prognosis for GBM patients remains dismal and quality of life is poor. Although new molecular pathways crucial to the biology and invasive ability of GBM are coming to light, translation of basic science achievements into clinical practice is slow. Optimal management requires a multidisciplinary approach and knowledge of potential complications arising from both disease and treatment. To help illustrate "where we are going" with GBM, we here include a detailed depiction of the molecular alterations underlying this fatal disease, as well as intensive research over the past two decades that has led to considerable advances in the understanding of basic GBM biology, pathogenesis and therapeutic approaches.

Human Brat ortholog TRIM3 is a tumor suppressor that regulates asymmetric cell division in glioblastoma

Cancer stem cells, capable of self-renewal and multipotent differentiation, influence tumor behavior through a complex balance of symmetric and asymmetric cell divisions. Mechanisms regulating the dynamics of stem cells and their progeny in human cancer are poorly understood. In Drosophila, mutation of brain tumor (brat) leads to loss of normal asymmetric cell division by developing neural cells and results in a massively enlarged brain composed of neuroblasts with neoplastic properties. Brat promotes asymmetric cell division and directs neural differentiation at least partially through its suppression on Myc. We identified TRIM3 (11p15.5) as a human ortholog of Drosophila brat and demonstrate its regulation of asymmetric cell division and stem cell properties of glioblastoma (GBM), a highly malignant human brain tumor. TRIM3 gene expression is markedly reduced in human GBM samples, neurosphere cultures, and cell lines and its reconstitution impairs growth properties in vitro and in vivo. TRIM3 expression attenuates stem-like qualities of primary GBM cultures, including neurosphere formation and the expression of stem cell markers CD133, Nestin, and Nanog. In GBM stem cells, TRIM3 expression leads to a greater percentage dividing asymmetrically rather than symmetrically. As with Brat in Drosophila, TRIM3 suppresses c-Myc expression and activity in human glioma cell lines. We also demonstrate a strong regulation of Musashi-Notch signaling by TRIM3 in GBM neurospheres and neural stem cells that may better explain its effect on stem cell dynamics. We conclude that TRIM3 acts as a tumor suppressor in GBM by restoring asymmetric cell division.

Pumilio-2 regulates translation of Nav1.6 to mediate homeostasis of membrane excitability

The ability to regulate intrinsic membrane excitability, to maintain consistency of action potential firing, is critical for stable neural circuit activity. Without such mechanisms, Hebbian-based synaptic plasticity could push circuits toward activity saturation or, alternatively, quiescence. Although now well documented, the underlying molecular components of these homeostatic mechanisms remain poorly understood. Recent work in the fruit fly, Drosophila melanogaster, has identified Pumilio (Pum), a translational repressor, as an essential component of one such mechanism. In response to changing synaptic excitation, Pum regulates the translation of the voltage-gated sodium conductance, leading to a concomitant adjustment in action potential firing. Although similar homeostatic mechanisms are operational in mammalian neurons, it is unknown whether Pum is similarly involved. In this study, we report that Pum2 is indeed central to the homeostatic mechanism regulating membrane excitability in rat visual cortical pyramidal neurons. Using RNA interference, we observed that loss of Pum2 leads to increased sodium current (I(Na)) and action potential firing, mimicking the response by these neurons to being deprived of synaptic depolarization. In contrast, increased synaptic depolarization results in increased Pum2 expression and subsequent reduction in INa and membrane excitability. We further show that Pum2 is able to directly bind the predominant voltage-gated sodium channel transcript (NaV1.6) expressed in these neurons and, through doing so, regulates translation of this key determinant of membrane excitability. Together, our results show that Pum2 forms part of a homeostatic mechanism that matches membrane excitability to synaptic depolarization in mammalian neurons.

Loss of heterozygosity of TRIM3 in malignant gliomas

BACKGROUND

Malignant gliomas are frequent primary brain tumors associated with poor prognosis and very limited response to conventional chemo- and radio-therapies. Besides sharing common growth features with other types of solid tumors, gliomas are highly invasive into adjacent brain tissue, which renders them particularly aggressive and their surgical resection inefficient. Therefore, insights into glioma formation are of fundamental interest in order to provide novel molecular targets for diagnostic purposes and potential anti-cancer drugs. Human Tripartite motif protein 3 (TRIM3) encodes a structural homolog of Drosophila brain tumor (brat) implicated in progenitor cell proliferation control and cancer stem cell suppression. TRIM3 is located within the loss of allelic heterozygosity (LOH) hotspot of chromosome segment 11p15.5, indicating a potential role in tumor suppression.

METHODS

Here we analyze 70 primary human gliomas of all types and grades and report somatic deletion mapping as well as single nucleotide polymorphism analysis together with quantitative real-time PCR of chromosome segment 11p15.5.

RESULTS

Our analysis identifies LOH in 17 cases (24%) of primary human glioma which defines a common 130 kb-wide interval within the TRIM3 locus as a minimal area of loss. We further detect altered genomic dosage of TRIM3 in two glioma cases with LOH at 11p15.5, indicating homozygous deletions of TRIM3.

CONCLUSION

Loss of heterozygosity of chromosome segment 11p15.5 in malignant gliomas suggests TRIM3 as a candidate brain tumor suppressor gene.

The brain tumor gene negatively regulates neural progenitor cell proliferation in the larval central brain of Drosophila

Brain development in Drosophila is characterized by two neurogenic periods, one during embryogenesis and a second during larval life. Although much is known about embryonic neurogenesis, little is known about the genetic control of postembryonic brain development. Here we use mosaic analysis with a repressible cell marker (MARCM) to study the role of the brain tumor (brat) gene in neural proliferation control and tumour suppression in postembryonic brain development of Drosophila. Our findings indicate that overproliferation in brat mutants is due to loss of proliferation control in the larval central brain and not in the optic lobe. Clonal analysis indicates that the brat mutation affects cell proliferation in a cell-autonomous manner and cell cycle marker expression shows that cells of brat mutant clones show uncontrolled proliferation, which persists into adulthood. Analysis of the expression of molecular markers, which characterize cell types in wild-type neural lineages, indicates that brat mutant clones comprise an excessive number of cells, which have molecular features of undifferentiated progenitor cells that lack nuclear Prospero (Pros). pros mutant clones phenocopy brat mutant clones in the larval central brain, and targeted expression of wild-type pros in brat mutant clones promotes cell cycle exit and differentiation of brat mutant cells, thereby abrogating brain tumour formation. Taken together, our results provide evidence that the tumour suppressor brat negatively regulates cell proliferation during larval central brain development of Drosophila, and suggest that Prospero acts as a key downstream effector of brat in cell fate specification and proliferation control.

The molluscan RING-finger protein L-TRIM is essential for neuronal outgrowth

The tripartite motif proteins TRIM-2 and TRIM-3 have been put forward as putative organizers of neuronal outgrowth and structural plasticity. Here, we identified a molluscan orthologue of TRIM-2/3, named L-TRIM, which is up-regulated during in vitro neurite outgrowth of central neurons. In adult animals, L-Trim mRNA is ubiquitously expressed at low levels in the central nervous system and in peripheral tissues. Central nervous system expression of L-Trim mRNA is increased during postnatal brain development and during in vitro and in vivo neuronal regeneration. In vitro double-stranded RNA knock-down of L-Trim mRNA resulted in a >70% inhibition of neurite outgrowth. Together, our data establish a crucial role for L-TRIM in developmental neurite outgrowth and functional neuronal regeneration and indicate that TRIM-2/3 family members may have evolutionary conserved functions in neuronal differentiation.

Transcriptional signature of an adult brain tumor in Drosophila

Background

Mutations and gene expression alterations in brain tumors have been extensively investigated, however the causes of brain tumorigenesis are largely unknown. Animal models are necessary to correlate altered transcriptional activity and tumor phenotype and to better understand how these alterations cause malignant growth. In order to gain insights into the in vivo transcriptional activity associated with a brain tumor, we carried out genome-wide microarray expression analyses of an adult brain tumor in Drosophila caused by homozygous mutation in the tumor suppressor gene brain tumor (brat).

Results

Two independent genome-wide gene expression studies using two different oligonucleotide microarray platforms were used to compare the transcriptome of adult wildtype flies with mutants displaying the adult brat^k06028 mutant brain tumor. Cross-validation and stringent statistical criteria identified a core transcriptional signature of brat^k06028 neoplastic tissue. We find significant expression level changes for 321 annotated genes associated with the adult neoplastic brat^k06028 tissue indicating elevated and aberrant metabolic and cell cycle activity, upregulation of the basal transcriptional machinery, as well as elevated and aberrant activity of ribosome synthesis and translation control. One fifth of these genes show homology to known mammalian genes involved in cancer formation.

Conclusion

Our results identify for the first time the genome-wide transcriptional alterations associated with an adult brain tumor in Drosophila and reveal insights into the possible mechanisms of tumor formation caused by homozygous mutation of the translational repressor brat.

Cloning and characterization of a novel RING-B-box-coiled-coil protein with apoptotic function

We have identified a novel RING-B-box-coiled-coil (RBCC) protein (MAIR for macrophage-derived apoptosis-inducing RBCC protein) that consists of an N-terminal RING finger, followed by a B-box zinc finger, a coiled-coil domain, and a B30.2 domain. MAIR mRNA was expressed widely in mouse tissues and was induced by macrophage colony-stimulating factor in murine peritoneal and bone marrow macrophages. MAIR protein initially showed a granular distribution predominantly in the cytoplasm. The addition of zinc to transfectants containing MAIR cDNA as part of a heavy metal-inducible vector caused apoptosis of the cells characterized by cell fragmentation; a reduction in mitochondrial membrane potential; activation of caspase-7, -8, and -9, but not caspase-3; and DNA degradation. We also found that the RING finger and coiled-coil domains were required for MAIR activity by analysis with deletion mutants.

Molecular cloning and characterization of a complementary DNA encoding sperm tail protein SHIPPO 1

Formation of the tail in developing sperm is a complex process involving the organization of the axoneme, transport of periaxonemal proteins from the cytoplasm to the tail, and assembly of the outer dense fibers and fibrous sheath. Although detailed morphological descriptions of these events are available, the molecular mechanisms remain to be fully elucidated. We have isolated a new gene, named shippo 1, from a haploid germ cell-specific cDNA library of mouse testis, and also its human orthologue (h-shippo 1). The isolated cDNA is 1.2 kilobases long, carrying a 762-base pair open reading frame that encodes SHIPPO 1, a sperm protein predicted to consist of 254 amino acids. The amino acid sequence includes 6 Pro-Gly-Pro repeats, which are also present in the human orthologue protein (hSHIPPO 1) as well as in 2 other newly reported proteins of Drosophila melanogaster. Transcription of shippo 1 is exclusively observed in haploid germ cells. Antibody raised against SHIPPO 1 identified a testis-specific M(r) 32 x 10(-3) band in Western blot analysis. The protein was further localized in the flagella of the elongated spermatids and along the entire length of the tail in mature sperm. SHIPPO 1 in sperm is resistant to treatment with nonionic detergents and coextracted with the cytoskeletal core proteins of the mouse sperm tail.

Expression of constructs of the neuronal isoform of myosin-Va interferes with the distribution of melanosomes and other vesicles in melanoma cells

Myosin-Va has been implicated in melanosome translocation, but the exact molecular mechanisms underlying this function are not known. In the dilute, S91 melanoma cells, melanosomes move to the cell periphery but do not accumulate in the tips of dendrites as occurs in wild-type B16 melanocytes; rather, they return and accumulate primarily at the pericentrosomal region in a microtubule-dependent manner. Expression of the full-length neuronal isoform of myosin-Va in S91 cells causes melanosomes to disperse, occupying a cellular area approximately twice that observed in non-transfected cells, suggesting a partial rescue of the dilute phenotype. Overexpression of the full tail domain in S91 cells is not sufficient to induce melanosome dispersion, rather it causes melanosomal clumping. Overexpression of the head and head-neck domains of myosin-Va in B16 cells does not alter the melanosome distribution. However, overexpression of the full tail domain in these cells induces melanosome aggregation and the appearance of tail-associated, aggregated particles or vesicular structures that exhibit variable degrees of staining for melanosomal and Golgi beta-COP markers, as well as colocalization with the endogenous myosin-Va. Altogether, the present data suggest that myosin-Va plays a role in regulating the direction of microtubule-dependent melanosome translocation, in addition to promoting the capture of melanosomes at the cell periphery as suggested by previous studies. These studies also reinforce the notion that myosin-V has a broader function in melanocytes by acting on vesicular targeting or intracellular protein trafficking.

Motor-cargo interactions: the key to transport specificity

Eukaryotic cells organize their cytoplasm by moving different organelles and macromolecular complexes along microtubules and actin filaments. These movements are powered by numerous motor proteins that must recognize their respective cargoes in order to function. Recently, several proteins that interact with motors have been identified by yeast two-hybrid and biochemical analyses, and their roles in transport are now being elucidated. In several cases, analysis of the binding partners helped to identify new transport pathways, new types of cargo, and transport regulated at the level of motor-cargo binding. We discuss here how different motors of the kinesin, dynein and myosin families recognize their cargo and how motor-cargo interactions are regulated.

PML protein isoforms and the RBCC/TRIM motif

PML is a component of a multiprotein complex, termed nuclear bodies, and the PML protein was originally discovered in patients suffering from acute promyelocytic leukaemia (APL). APL is associated with a reciprocal chromosomal translocation of chromosomes 15 and 17, which results in a fusion protein comprising PML and the retinoic acid receptor alpha. The PML genomic locus is approximately 35 kb and is subdivided into nine exons. A large number of alternative spliced transcripts are synthesized from the PML gene, resulting in a variety of PML proteins ranging in molecular weight from 48-97 kDa. In this review we summarize the data on the known PML isoforms and splice variants and present a new unifying nomenclature. Although, the function/s of the PML variants are unclear, all PML isoforms contain an identical N-terminal region, suggesting that these sequences are indispensable for function, but differ in their C-terminal sequences. The N-terminal region harbours a RING-finger, two B-boxes and a predicted alpha-helical Coiled-Coil domain, that together form the RBCC/TRIM motif found in a large family of proteins. In PML this motif is essential for PML nuclear body formation in vivo and PML-homo and hetero interactions conferring growth suppressor, apoptotic and anti-viral activities. In APL oligomerization mediated by the RBCC/TRIM motif is essential for the transformation potential of the PML-RARalpha fusion protein.