Dimerization choice and alternative functions of ZBTB transcription factors

Mechanistic Insights Into the Assembly of Functional CRL3 Dimeric Complexes

The assembly of Cullin3-based RING E3 ubiquitin ligase (CRL3) complexes is orchestrated in two consecutive steps: the formation of the dimeric BTB domain core and the recruitment of CUL3-RBX1 subunits. Each step is tightly regulated to ensure the formation of complete and functional dimeric CRL3s. The first assembly step is regulated by two mechanisms: "co-co assembly" and proteasome-dependent degradation of aberrant heterodimers. The second step is facilitated by a conserved CUL3 N-terminal assembly (NA) motif. The CUL3 NA motif contributes to the assembly of CRL3s in two aspects: interacting with both BTB domain-containing protein protomers to facilitate complete dimeric assembly, and enhancing the stability of CRL3s by overcoming the tensions generated by conformational entropy during ubiquitin transfer. Given that all Cullin proteins contain N-terminal extensions, we postulate that these extensions, similar to the CUL3 NA motif-contributed assembly, play an important role in the functional regulation of CRLs and thus warrant further investigation.

Genetic susceptibility to lung squamous cell carcinoma: new insights on 9q33.2 variants and tobacco smoking

Genome-wide association studies (GWAS) have identified over 60 susceptibility loci for lung cancer, yet the biological mechanisms underlying these associations remain largely unknown, particularly for lung squamous cell carcinoma (LUSC). Here, we integrated data from 3890 LUSC cases and 13 328 controls of Chinese descent, and performed a conditional analysis to explore independent genetic variants and analyzed the interaction between the genetic variants and smoking. Our study was the first to identify a specific association between genetic variants in the 9q33.2 region and increased risk of LUSC in smokers. After adjusting for the tag SNP rs4573350 in 9q33.2, no additional significant genetic variants were found. However, significant additive (RERI = 1.66, 95% CI: 1.17-2.22, AP = 0.26, 95% CI: 0.19-0.33) and multiple interactions (OR = 1.30, 95% CI: 1.08-1.56, P = 5.40 × 10-3) were observed between rs4573350 and smoking. Compared to nonsmokers with the CC genotype, smokers with the CT/TT genotype showed an increased risk of 6.29-fold (95% CI: 5.46-7.23, P = 2.00 × 10-16). Functional annotation identified rs4573350 as the strongest functional variant within the linkage disequilibrium block. Biological experiments confirmed that the combined exposure to the T allele of rs4573350 and cigarette smoke extract promotes the expression of the ZBTB26 by modulating the binding ability of the transcription factor FOXA1. Furthermore, ZBTB26 was found to regulate tumorigenesis of LUSC both in vitro and in vivo by affecting the expression of PCNA, which is involved in cell cycle and promotes tumorigenesis of LUSC.

LATS1-modulated ZBTB20 perturbing cartilage matrix homeostasis contributes to early-stage osteoarthritis

Osteoarthritis (OA) is one of the most common degenerative joint diseases in the elderly, increasing in prevalence and posing a substantial socioeconomic challenge, while no disease-modifying treatments available. Better understanding of the early molecular events will benefit the early-stage diagnosis and clinical therapy. Here, we observed the nucleus accumulation of ZBTB20, a member of ZBTB-protein family, in the chondrocytes of early-stage OA. Chondrocytes-specific depletion of Zbtb20 in adult mice attenuated DMM-induced OA progress, restored the balance of extracellular matrix anabolism and catabolism. The NF-κB signaling mediated disturbance of ECM maintenance by ZBTB20 requires its suppression of Pten and consequent PI3K-Akt signaling activation. Furthermore, the subcellular localization of ZBTB20 was modulated by the kinase LATS1. Independent approaches to modulating ZBTB20 via utilizing TRULI and DAPA can restore ECM homeostasis, improving the abnormal behavior and moderating cartilage degeneration. The compounds TRULI and DAPA modulating ZBTB20 may serve as anti-OA drugs.

Structural studies of KCTD1 and its disease-causing mutant P20S provide insights into the protein function and misfunction

Members of the KCTD protein family play key roles in fundamental physio-pathological processes including cancer, neurodevelopmental/neuropsychiatric, and genetic diseases. Here, we report the crystal structure of the KCTD1 P20S mutant, which causes the scalp-ear-nipple syndrome, and molecular dynamics (MD) data on the wild-type protein. Surprisingly, the structure unravels that the N-terminal region, which precedes the BTB domain (preBTB) and bears the disease-associated mutation, adopts a folded polyproline II (PPII) state. The KCTD1 pentamer is characterized by an intricate architecture in which the different subunits mutually exchange domains to generate a closed domain swapping motif. Indeed, the BTB of each chain makes peculiar contacts with the preBTB and the C-terminal domain (CTD) of an adjacent chain. The BTB-preBTB interaction consists of a PPII-PPII recognition motif whereas the BTB-CTD contacts are mediated by an unusual (+/-) helix discontinuous association. The inspection of the protein structure, along with the data emerged from the MD simulations, provides an explanation of the pathogenicity of the P20S mutation and unravels the role of the BTB-preBTB interaction in the insurgence of the disease. Finally, the presence of potassium bound to the central cavity of the CTD pentameric assembly provides insights into the role of KCTD1 in metal homeostasis.

Engineering circular RNA for molecular and metabolic reprogramming

The role of messenger RNA (mRNA) in biological systems is extremely versatile. However, it's extremely short half-life poses a fundamental restriction on its application. Moreover, the translation efficiency of mRNA is also limited. On the contrary, circular RNAs, also known as circRNAs, are a common and stable form of RNA found in eukaryotic cells. These molecules are synthesized via back-splicing. Both synthetic circRNAs and certain endogenous circRNAs have the potential to encode proteins, hence suggesting the potential of circRNA as a gene expression machinery. Herein, we aim to summarize all engineering aspects that allow exogenous circular RNA (circRNA) to prolong the time that proteins are expressed from full-length RNA signals. This review presents a systematic engineering approach that have been devised to efficiently assemble circRNAs and evaluate several aspects that have an impact on protein production derived from. We have also reviewed how optimization of the key components of circRNAs, including the topology of vector, 5' and 3' untranslated sections, entrance site of the internal ribosome, and engineered aptamers could be efficiently impacting the translation machinery for molecular and metabolic reprogramming. Collectively, molecular and metabolic reprogramming present a novel way of regulating distinctive cellular features, for instance growth traits to neoplastic cells, and offer new possibilities for therapeutic inventions.

Co-translational Assembly Pathways of Nuclear Multiprotein Complexes Involved in the Regulation of Gene Transcription

Most factors that regulate gene transcription in eukaryotic cells are multimeric, often large, protein complexes. The understanding of the biogenesis pathways of such large and heterogeneous protein assemblies, as well as the dimerization partner choice among transcription factors, is crucial to interpret and control gene expression programs and consequent cell fate decisions. Co-translational assembly (Co-TA) is thought to play key roles in the biogenesis of protein complexes by directing complex formation during protein synthesis. In this review we discuss the principles of Co-TA with a special focus for the assembly of transcription regulatory complexes. We outline the expected molecular advantages of establishing co-translational interactions, pointing at the available, or missing, evidence for each of them. We hypothesize different molecular mechanisms based on Co-TA to explain the allocation "dilemma" of paralog proteins and subunits shared by different transcription complexes. By taking as a paradigm the different assembly pathways employed by three related transcription regulatory complexes (TFIID, SAGA and ATAC), we discuss alternative Co-TA strategies for nuclear multiprotein complexes and the widespread - yet specific - use of Co-TA for the formation of nuclear complexes involved in gene transcription. Ultimately, we outlined a series of open questions which demand well-defined lines of research to investigate the principles of gene regulation that rely on the coordinated assembly of protein complexes.

Evaluation of Clinical and Immunological Alterations Associated with ICF Syndrome

PURPOSE

Immunodeficiency with centromeric instability and facial anomalies (ICF) syndrome is a rare autosomal recessive combined immunodeficiency. The detailed immune responses are not explored widely. We investigated known and novel immune alterations in lymphocyte subpopulations and their association with clinical symptoms in a well-defined ICF cohort.

METHODS

We recruited the clinical findings from twelve ICF1 and ICF2 patients. We performed detailed immunological evaluation, including lymphocyte subset analyses, upregulation, and proliferation of T cells. We also determined the frequency of circulating T follicular helper (cTFH) and regulatory T (Treg) cells and their subtypes by flow cytometry.

RESULTS

There were ten ICF1 and two ICF2 patients. We identified two novel homozygous missense mutations in the ZBTB24 gene. Respiratory tract infections were the most common recurrent infections among the patients. Gastrointestinal system (GIS) involvements were observed in seven patients. All patients received intravenous immunoglobulin replacement therapy and antibacterial prophylaxis; two died during the follow-up period. Immunologically, CD4+ T-cell counts, percentages of recent thymic emigrant T cells, and naive CD4+ T decreased in two, five, and four patients, respectively. Impaired T-cell proliferation and reduced CD25 upregulation were detected in all patients. These changes were more prominent in CD8+ T cells. GIS involvements negatively correlated with CD3+ T-, CD3+CD4+ T-, CD16+CD56+ NK-cell counts, and CD4+/CD8+ T-cell ratios. Further, we observed expanded cTFH cells and reduced Treg and follicular regulatory T cells with a skewing to a TH2-like phenotype in all tested subpopulations.

CONCLUSION

The ICF syndrome encompasses various manifestations affecting multiple end organs. Perturbed T-cell responses with increased cTFH and decreased Treg cells may provide further insight into the immune aberrations observed in ICF syndrome.