SKIP is an indispensable factor for Caenorhabditis elegans development

SKIP Silencing Decreased Disease Resistance Against Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000 in Tomato

SKIP, a component of the spliceosome, is involved in numerous signaling pathways. However, there is no direct genetic evidence supporting the function of SKIP in defense responses. In this paper, two SKIPs, namely, SlSKIP1a and SlSKIP1b, were analyzed in tomato. qRT-PCR analysis showed that the SlSKIP1b expression was triggered via Pseudomonas syringae pv. tomato (Pst) DC3000 and Botrytis cinerea (B. cinerea), together with the defense-associated signals. In addition, the functions of SlSKIP1a and SlSKIP1b in disease resistance were analyzed in tomato through the virus-induced gene silencing (VIGS) technique. VIGS-mediated SlSKIP1b silencing led to increased accumulation of reactive oxygen species (ROS), along with the decreased expression of defense-related genes (DRGs) after pathogen infection, suggesting that it reduced B. cinerea and Pst DC3000 resistance. There was no significant difference in B. cinerea and Pst DC3000 resistance in TRV-SlSKIP1a-infiltrated plants compared with the TRV-GUS-silencing counterparts. As suggested by the above findings, SlSKIP1b plays a vital role in disease resistance against pathogens possibly by regulating the accumulation of ROS as well as the expression of DRGs.

Binding Nemo

Article highlight based on "SNW1 interacts with IKKγ to positively regulate antiviral innate immune responses against influenza A virus infection" by Qiao et al.

Insight into the possible mechanism of the summer diapause of Delia antiqua (Diptera: Anthomyiidae) through digital gene expression analysis

The onion fly, Delia antiqua, is a major underground agricultural pest that can enter pupal diapause in the summer and winter seasons. However, little is known about its molecular regulation due to the lack of genomic resources. To gain insight into the possible mechanism of summer diapause (SD), high-throughput RNA-Seq data were generated from non-diapause (ND) and SD (initial, maintenance and quiescence phase) pupae. Three pair-wise comparisons were performed and identified, 1380, 1471 and 435, and were significantly regulated transcripts. Further analysis revealed that the enrichment of several functional terms related to juvenile hormone regulation, cell cycle, carbon hydrate and lipid metabolism, innate immune and stress responses, various signalling transductions, ubiquitin-dependent proteosome, and variation in cuticular and cytoskeleton components were found between ND and SD and between different phases of SD. Global characterization of transcriptome profiling between SD and ND contributes to the in-depth elucidation of the molecular mechanism of SD. Our results also offer insights into the evolution of insect diapause and support the importance of using the onion fly as a model to compare the molecular regulation events of summer and winter diapauses.

SKIP and BIR-1/Survivin have potential to integrate proteome status with gene expression

SKIP and BIR are evolutionarily conserved proteins; SKIP (SKP-1) is a known transcription and splicing cofactor while BIR-1/Survivin regulates cell division, gene expression and development. Their loss of function induces overlapping developmental phenotypes. We searched for SKP-1 and BIR-1 interaction on protein level using yeast two-hybrid screens and identified partially overlapping categories of proteins as SKIP-1 and BIR-1 interactors. The interacting proteins included ribosomal proteins, transcription factors, translation factors and cytoskeletal and motor proteins suggesting involvement in multiple protein complexes. To visualize the effect of BIR-1 on the proteome in Caenorhabditis elegans we induced a short time pulse BIR-1 overexpression in synchronized L1 larvae. This led to a dramatic alteration of the whole proteome pattern indicating that BIR-1 alone has the capacity to alter the chromatographic profile of many target proteins including proteins found to be interactors in yeast two hybrid screens. The results were validated for ribosomal proteins RPS3 and RPL5, non-muscle myosin and TAC-1, a transcription cofactor and a centrosome associated protein. Together, these results suggest that SKP-1 and BIR-1 are multifunctional proteins that form multiple protein complexes in both shared and distinct pathways and have the potential to connect proteome signals with the regulation of gene expression.

BIOLOGICAL SIGNIFICANCE

The genomic organization of the genes encoding BIR-1 and SKIP (SKP-1) in C. elegans have suggested that these two factors, each evolutionarily conserved, have related functions. However, these functional connections have remained elusive and underappreciated in light of limited information from C. elegans and other biological systems. Our results provide further evidence for a functional link between these two factors and suggest they may transmit proteome signals towards the regulation of gene expression.

Knockdown of a novel G-protein pathway suppressor 2 (GPS2) leads to shrimp mortality by exuvial entrapment during ecdysis

A novel G-protein pathway suppressor 2 (GPS2) has been identified from hemocytes of the whiteleg shrimp Penaeus vannamei (Pv) and appears to play a role in ecdysis. The full-length of PvGPS2 cDNA consisted of a 1230-bp open reading frame, encoding 409 deduced amino acids with significant sequence homology to GPS2 sequences of crustaceans and insects. RT-PCR revealed that PvGPS2 was expressed in all P. vannamei tissues examined, but that expression was molt stage specific in eyestalk tissue. Relative expression was higher in the period before molting (i.e., intermolt and pre-molt stages) than in the post-molt stage. When double-stranded RNA (dsRNA)-mediated RNA interference was employed to inhibit PvGPS2 formation in shrimp, it led to significant mortality due to unsuccessful separation of new cuticle from old cuticle (exuvial entrapment) during ecdysis.

Ski-interacting protein (SKIP) interacts with androgen receptor in the nucleus and modulates androgen-dependent transcription

Background

The androgen receptor (AR) is a member of the nuclear receptor (NR) superfamily of ligand-inducible DNA transcription factors, and is the major mediator of male sexual development, prostate growth and the pathogenesis of prostate cancer. Cell and gene specific regulation by the AR is determined by availability of and interaction with sets of key accessory cofactors. Ski-interacting protein (SKIP; SNW1, NCOA62) is a cofactor shown to interact with several NRs and a diverse range of other transcription factors. Interestingly, SKIP as part of the spliceosome is thought to link mRNA splicing with transcription. SKIP has not been previously shown to interact with the AR.

Results

The aim of this study was to investigate whether SKIP interacts with the AR and modulates AR-dependent transcription. Here, we show by co-immunoprecipitation experiments that SKIP is in a complex with the AR. Moreover, SKIP increased 5α-dihydrotestosterone (DHT) induced N-terminal/C-terminal AR interaction from 12-fold to almost 300-fold in a two-hybrid assay, and enhanced AR ligand-independent AF-1 transactivation. SKIP augmented ligand- and AR-dependent transactivation in PC3 prostate cancer cells. Live-cell imaging revealed a fast (half-time=129 s) translocation of AR from the cytoplasm to the nucleus upon DHT-stimulation. Förster resonance energy transfer (FRET) experiments suggest a direct AR-SKIP interaction in the nucleus upon translocation.

Conclusions

Our results suggest that SKIP interacts with AR in the nucleus and enhances AR-dependent transactivation and N/C-interaction supporting a role for SKIP as an AR co-factor.

GmGBP1, a homolog of human ski interacting protein in soybean, regulates flowering and stress tolerance in Arabidopsis

BACKGROUND

SKIP is a transcription cofactor in many eukaryotes. It can regulate plant stress tolerance in rice and Arabidopsis. But the homolog of SKIP protein in soybean has been not reported up to now.

RESULTS

In this study, the expression patterns of soybean GAMYB binding protein gene (GmGBP1) encoding a homolog of SKIP protein were analyzed in soybean under abiotic stresses and different day lengths. The expression of GmGBP1 was induced by polyethyleneglycol 6000, NaCl, gibberellin, abscisic acid and heat stress. GmGBP1 had transcriptional activity in C-terminal. GmGBP1 could interact with R2R3 domain of GmGAMYB1 in SKIP domain to take part in gibberellin flowering pathway. In long-day (16 h-light) condition, transgenic Arabidopsis with the ectopic overexpression of GmGBP1 exhibited earlier flowering and less number of rosette leaves; Suppression of AtSKIP in Arabidopsis resulted in growth arrest, flowering delay and down-regulation of many flowering-related genes (CONSTANS, FLOWERING LOCUS T, LEAFY); Arabidopsis myb33 mutant plants with ectopic overexpression of GmGBP1 showed the same flowering phenotype with wild type. In short-day (8 h-light) condition, transgenic Arabidopsis plants with GmGBP1 flowered later and showed a higher level of FLOWERING LOCUS C compared with wild type. When treated with abiotic stresses, transgenic Arabidopsis with the ectopic overexpression of GmGBP1 enhanced the tolerances to heat and drought stresses but reduced the tolerance to high salinity, and affected the expressions of several stress-related genes.

CONCLUSIONS

In Arabidopsis, GmGBP1 might positively regulate the flowering time by affecting CONSTANS, FLOWERING LOCUS T, LEAFY and GAMYB directly or indirectly in photoperiodic and gibberellin pathways in LDs, but GmGBP1 might represse flowering by affecting FLOWERING LOCUS C and SHORT VEGETATIVE PHASE in autonomous pathway in SDs. GmGBP1 might regulate the activity of ROS-eliminating to improve the resistance to heat and drought but reduce the high-salinity tolerance.

Xenopus skip modulates Wnt/beta-catenin signaling and functions in neural crest induction

The beta-catenin-lymphoid enhancer factor (LEF) protein complex is the key mediator of canonical Wnt signaling and initiates target gene transcription upon ligand stimulation. In addition to beta-catenin and LEF themselves, many other proteins have been identified as necessary cofactors. Here we report that the evolutionally conserved splicing factor and transcriptional co-regulator, SKIP/SNW/NcoA62, forms a ternary complex with LEF1 and HDAC1 and mediates the repression of target genes. Loss-of-function studies showed that SKIP is obligatory for Wnt signaling-induced target gene transactivation, suggesting an important role of SKIP in the canonical Wnt signaling. Consistent with its involvement in beta-catenin signaling, the C-terminally truncated forms of SKIP are able to stabilize beta-catenin and enhance Wnt signaling. In Xenopus embryos, both overexpression and knockdown of Skip lead to reduced neural crest induction, consistent with down-regulated Wnt signaling in both cases. Our results indicate that SKIP is a novel component of the beta-catenin transcriptional complex.

A homolog of human ski-interacting protein in rice positively regulates cell viability and stress tolerance

Abiotic stresses are major limiting factors for growth, development, and productivity of crop plants. Here, we report on OsSKIPa, a rice homolog of human Ski-interacting protein (SKIP) that can complement the lethal defect of the knockout mutant of SKIP homolog in yeast and positively modulate cell viability and stress tolerance of rice. Suppression of OsSKIPa in rice resulted in growth arrest and reduced cell viability. The expression OsSKIPa is induced by various abiotic stresses and phytohormone treatments. Transgenic rice overexpressing OsSKIPa exhibited significantly improved growth performance in the medium containing stress agents (abscisic acid, salt, or mannitol) and drought resistance at both the seedling and reproductive stages. The OsSKIPa-overexpressing rice showed significantly increased reactive oxygen species-scavenging ability and transcript levels of many stress-related genes, including SNAC1 and rice homologs of CBF2, PP2C, and RD22, under drought stress conditions. More than 30 OsSKIPa-interacting proteins were identified, but most of these proteins have no matches with the reported SKIP-interacting proteins in animals and yeast. Together, these data suggest that OsSKIPa has evolved a specific function in positive modulation of stress resistance through transcriptional regulation of diverse stress-related genes in rice.

NHR-40, a Caenorhabditis elegans supplementary nuclear receptor, regulates embryonic and early larval development

Nuclear hormone receptors (NHRs) are important regulators of development and metabolism in animal species. They are characterized by the ability to regulate gene expression in response to the binding of small hydrophobic molecules, hormones, metabolites, and xenobiotics. The Caenorhabditis elegans genome contains 284 sequences that share homology to vertebrate and insect NHRs, a surprisingly large number compared with other species. The majority of C. elegans NHRs are nematode-specific and are referred to as supplementary nuclear receptors (supnrs) that are thought to have originated by duplications of an ancient homolog of vertebrate HNF4. Here, we report on the function of NHR-40, a member of a subgroup of 18 Caenorhabditis elegans supnrs that share DNA-binding domain sequence CNGCKT. NHR-40 is expressed from at least two promoters, generates at least three transcripts, and is detectable in pharyngeal, body wall, and sex muscles as well as in a subset of neurons. The downregulation of nhr-40 by RNAi, or a mutant with an intronic region deletion, results in late embryonic and early larval arrest with defects in elongation and morphogenesis. The nhr-40 loss of function phenotype includes irregular development of body wall muscle cells and impaired movement and coordination resembling neuromuscular affection. NHR-40 joins the list of C. elegans NHRs that regulate development and suggests that members of extensive nematode supnr family have acquired varied and novel functions during evolution.

Echinococcus multilocularis: Cloning and characterization of a member of the SNW/SKIP family of transcriptional coregulators

We have isolated a cDNA from the fox-tapeworm Echinococcus multilocularis that encodes EmSkip, a novel member of the SNW/SKIP family of transcriptional coregulators. EmSkip displays significant amino acid sequence homologies to already known members of the protein family and contains all the characteristic amino acid residues at their corresponding positions. RT-PCR experiments showed that the EmSkip encoding gene, emskip, is expressed in the Echinococcus larval stages metacestode and protoscolex during an infection of the intermediate host. By yeast two-hybrid analyses, EmSkip was found to be capable of forming homodimers in vivo. Furthermore, EmSkip was found to interact with EmSmadA and EmSmadB, two previously identified TGF-beta/BMP signal transducers of E. multilocularis, indicating a role of this protein in TGF-beta signaling processes in the parasite. In view of the role played by SNW/SKIP proteins in splicing mechanisms and intracellular signaling, the data presented herein should facilitate the identification of Echinococcus factors involved in such processes.

Functional genomic analysis of C. elegans molting

Although the molting cycle is a hallmark of insects and nematodes, neither the endocrine control of molting via size, stage, and nutritional inputs nor the enzymatic mechanism for synthesis and release of the exoskeleton is well understood. Here, we identify endocrine and enzymatic regulators of molting in C. elegans through a genome-wide RNA-interference screen. Products of the 159 genes discovered include annotated transcription factors, secreted peptides, transmembrane proteins, and extracellular matrix enzymes essential for molting. Fusions between several genes and green fluorescent protein show a pulse of expression before each molt in epithelial cells that synthesize the exoskeleton, indicating that the corresponding proteins are made in the correct time and place to regulate molting. We show further that inactivation of particular genes abrogates expression of the green fluorescent protein reporter genes, revealing regulatory networks that might couple the expression of genes essential for molting to endocrine cues. Many molting genes are conserved in parasitic nematodes responsible for human disease, and thus represent attractive targets for pesticide and pharmaceutical development.

The authors use a genome-wide RNA-interference screen to identify and characterize genes involved in C. elegans molting. They investigate regulatory networks involved in molting, lending important new insights into this complex process.

The death domain-associated protein modulates activity of the transcription co-factor Skip/NcoA62

Death domain-associated protein (Daxx) regulates both transcription and apoptosis. The role of Daxx in transcription is not well understood. Here, we show that Daxx interacts with Skip/NcoA62, a transcription cofactor that modulates the activity of oncoproteins including Ski and NotchIC. Daxx strongly binds with Skip both in vitro and in mammalian cells. This interaction is mediated by the PAH2 domain of Daxx and the highly conserved SNW domain of Skip. Daxx partially co-localizes with Skip in vivo and changes the cellular distribution of Skip. In addition, Skip represses transcription when tethered to a promoter, and Daxx antagonizes this activity. Furthermore, Skip is phosphorylated at serine 224 in its SNW domain. These results suggest a novel function of Daxx in transcription regulation through alteration of the cellular localization of Skip.

A human splicing factor, SKIP, associates with P-TEFb and enhances transcription elongation by HIV-1 Tat

HIV-1 Tat binds human CyclinT1 and recruits the CDK9/P-TEFb complex to the viral TAR RNA in a step that links RNA polymerase II (RNAPII) C-terminal domain (CTD) Ser 2 phosphorylation with transcription elongation. Previous studies have suggested a connection between Tat and pre-mRNA splicing factors. Here we show that the splicing-associated c-Ski-interacting protein, SKIP, is required for Tat transactivation in vivo and stimulates HIV-1 transcription elongation, but not initiation, in vitro. SKIP associates with CycT1:CDK9/P-TEFb and Tat:P-TEFb complexes in nuclear extracts and interacts with recombinant Tat:P-TEFb:TAR RNA complexes in vitro, indicating that it may act through nascent RNA to overcome pausing by RNAPII. SKIP also associates with U5snRNP proteins and tri-snRNP110K in nuclear extracts, and facilitates recognition of an alternative Tat-specific splice site in vivo. The effects of SKIP on transcription elongation, binding to P-TEFb, and splicing are mediated through the SNW domain. HIV-1 Tat transactivation is accompanied by the recruitment of P-TEFb, SKIP, and tri-snRNP110K to the integrated HIV-1 promoter in vivo, whereas the U5snRNPs associate only with the transcribed coding region. These findings suggest that SKIP plays independent roles in transcription elongation and pre-mRNA splicing.

Mastermind recruits CycC:CDK8 to phosphorylate the Notch ICD and coordinate activation with turnover

Notch signaling releases the Notch receptor intracellular domain (ICD), which complexes with CBF1 and Mastermind (MAM) to activate responsive genes. We previously reported that MAM interacts with CBP/p300 and promotes hyperphosphorylation and degradation of the Notch ICD in vivo. Here we show that CycC:CDK8 and CycT1:CDK9/P-TEFb are recruited with Notch and associated coactivators (MAM, SKIP) to the HES1 promoter in signaling cells. MAM interacts directly with CDK8 and can cause it to localize to subnuclear foci. Purified recombinant CycC:CDK8 phosphorylates the Notch ICD within the TAD and PEST domains, and expression of CycC:CDK8 strongly enhances Notch ICD hyperphosphorylation and PEST-dependent degradation by the Fbw7/Sel10 ubiquitin ligase in vivo. Point mutations affecting conserved Ser residues within the ICD PEST motif prevent hyperphosphorylation by CycC:CDK8 and stabilize the ICD in vivo. These findings suggest a role for MAM and CycC:CDK8 in the turnover of the Notch enhancer complex at target genes.

Differential effects of the Ski-interacting protein (SKIP) on differentiation induced by transforming growth factor-β1 and bone morphogenetic protein-2 in C2C12 cells

The transforming growth factor-beta (TGF-beta) and bone morphogenetic proteins (BMP) are key regulatory factors that affect many critical cellular events in growth and development. Recently, we have shown that the Ski-interacting protein (SKIP) can augment TGF-beta signals. Here, we extended these studies by examining the biologic consequences of SKIP overexpression on TGF-beta1 and BMP-2 signals in C2C12 cells. C2C12 myoblasts differentiate into myotubes when the media is depleted of mitogenic factors, and TGF-beta1 inhibits this myotube formation. BMP-2 not only inhibits the myotube formation, but also induces C2C12 cells to differentiate into osteoblasts. Here, we show that SKIP-overexpressing C2C12 cells treated with TGF-beta1 or BMP-2 displayed no differences in comparison to vector control cells in their ability to form myotubes or in the expression of the myogenic markers myosin heavy chain-1 and myogenin. Unexpectedly, SKIP-overexpressing C2C12 cells treated with BMP-2 displayed suppressed expression of the induced osteoblast markers alkaline phosphatase, osteocalcin, and the transcription factor Runx2. Lastly, SKIP could repress transcription induced by BMP-2 in luciferase reporter assays done in C2C12 cells. These data show that SKIP has specific inhibitory effects on BMP-2-induced differentiation and implicate SKIP to be a novel regulator of the differentiation programming induced by TGF-beta signals.

Emerging insights into the coactivator role of NCoA62/SKIP in Vitamin D-mediated transcription

NCoA62/SKIP was discovered as a nuclear protein that interacts with the Vitamin D receptor (VDR) and the SKI oncoprotein. NCoA62/SKIP expresses properties consistent with other nuclear receptor transcriptional coactivator proteins. For example, NCoA62/SKIP interacts selectively with the VDR-RXR heterodimer, it forms a ternary complex with liganded VDR and steroid receptor coactivator (SRC) proteins, and it synergizes with SRCs to augment 1,25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)]- and VDR-activated transcription. Chromatin immunoprecipitation studies show that NCoA62/SKIP is recruited in a 1,25-(OH)(2)D(3)-dependent manner to native Vitamin D responsive gene promoters and it enters these promoter complexes after VDR and SRC entry. This suggests that NCoA62/SKIP functions at a distal step in the transactivation process. Recent studies indicate that NCoA62/SKIP is a component of the spliceosome machinery and interacts with important splicing factors such as prp8 and the U5 200kDa helicase. Functional studies also support an involvement of NCoA62/SKIP in mRNA splicing. Collectively, these data suggest a pivotal role for NCoA62/SKIP in coupling transcriptional regulation by VDR to RNA splicing. They further solidify an important role for VDR/NR-interactors downstream of the transcription process in determining the overall response of Vitamin D and steroid hormone regulated genes.

Ski-interacting protein, a bifunctional nuclear receptor coregulator that interacts with N-CoR/SMRT and p300

Ski-interacting protein (SKIP), a vitamin D receptor (VDR) coactivator, also functions as a repressor in Notch signalling in association with the corepressor SMRT. Here we show that SKIP bifunctionally modulates (activates or represses) Retinoid-X receptor (RXR)- and VDR-dependent gene transcription in a cell line-specific manner, with activation in CV-1 and repression in P19 cells. The coactivator function of SKIP in these cells appeared to correlate with the relative level and ratio of expression of N-CoR and p300, with greater SKIP activation in higher p300-expressing and lower N-CoR-expressing cell-lines. C-terminal deletion of SKIP (delta334-536 aa) was associated with strong activation in both CV-1 and P19 cells. The corepressors N-CoR and SMRT and the coregulator p300 interacted with SKIP through the same N-terminal region (1-200 aa). Overall these results suggest that transcriptional action of SKIP may depend on distinct functional domains and cell line-specific interactions with both corepressors and coactivators.

Cloning and expression of cDNA for a luciferase from the marine copepod Metridia longa. A novel secreted bioluminescent reporter enzyme

Metridia longa is a marine copepod from which a blue bioluminescence originates as a secretion from epidermal glands in response to various stimuli. We demonstrate that Metridia luciferase is specific for coelenterazine to produce blue light (lambda(max) = 480 nm). Using an expression cDNA library and functional screening, we cloned and sequenced the cDNA encoding the Metridia luciferase. The cDNA is an 897-bp fragment with a 656-bp open reading frame, which encodes a 219-amino acid polypeptide with a molecular weight of 23,885. The polypeptide contains an N-terminal signal peptide of 17 amino acid residues for secretion. On expression of the Metridia luciferase gene in mammalian Chinese hamster ovary cells the luciferase is detected in the culture medium confirming the existence of a naturally occurring signal peptide for secretion in the cloned luciferase. The novel secreted luciferase was tested in a practical assay application in which the activity of A2a and NPY2 G-protein-coupled receptors was detected. These results clearly suggest that the secreted Metridia luciferase is well suited as a reporter for monitoring gene expression and, in particular, for the development of novel ultrahigh throughput screening technologies.

Nuclear poly(A)-binding protein PABPN1 is associated with RNA polymerase II during transcription and accompanies the released transcript to the nuclear pore

The nuclear poly(A)-binding protein, PABPN1, has been previously shown to regulate mRNA poly(A) tail length and to interact with selected proteins involved in mRNA synthesis and trafficking. To further understand the role of PABPN1 in mRNA metabolism, we used cryo-immunoelectron microscopy to determine the fate of PABPN1 at various stages in the assembly and transport of the Chironomus tentans salivary gland Balbiani ring (BR) mRNA ribonucleoprotein (mRNP) complex. PABPN1 is found on BR mRNPs within the nucleoplasm as well as on mRNPs docked at the nuclear pore. Very little PABPN1 is detected on the cytoplasmic side of the nuclear envelope, suggesting that PABPN1 is displaced from mRNPs during or shortly after passage through the nuclear pore. Surprisingly, we also find PABPN1 associated with RNA polymerase II along the chromatin axis of the BR gene. Our results suggest that PABPN1 binds to the polymerase before, at, or shortly after the start of transcription, and that the assembly of PABPN1 onto the poly(A) tail may be coupled to transcription. Furthermore, PABPN1 remains associated with the released BR mRNP until the mRNP is translocated from the nucleus to the cytoplasm.

BIR-1, a Caenorhabditis elegans homologue of Survivin, regulates transcription and development

bir-1, a Caenorhabditis elegans inhibitor-of-apoptosis gene homologous to Survivin is organized in an operon with the transcription cofactor C. elegans SKIP (skp-1). Because genes arranged in operons are frequently linked functionally, we have asked whether BIR-1 also functions in transcription. bir-1 inhibition resulted in multiple developmental defects that overlapped with C. elegans SKIP loss-of-function phenotypes: retention of eggs, dumpy, movement defects, and lethality. bir-1 RNA-mediated interference decreased expression of several gfp transgenes and the endogenous genes dpy-7 and hlh-1. Immunoblot analysis revealed decreased phosphoacetylated histones in bir-1 RNA-mediated interference-treated worms. In a heterologous transfection system, BIR-1 augments thyroid hormone-regulated transcription and has an additive effect with SKIP. These results show that BIR-1 functions in the regulation of transcription and development.