Drosophila p53 isoforms have overlapping and distinct functions in germline genome integrity and oocyte quality control.
Ontology highlight
ABSTRACT:
SUBMITTER: Chakravarti A
PROVIDER: S-EPMC8758136 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:The SIN3 corepressor serves as a scaffold for the assembly of histone deacetylase (HDAC) complexes. SIN3 and its associated HDAC have been shown to have critical roles in both development and the regulation of cell cycle progression. Although multiple SIN3 isoforms have been reported in simple to complex eukaryotic organisms, the mechanisms by which such isoforms regulate specific biological processes are still largely uncharacterized. To gain insight into how SIN3 isoform-specific function contributes to the growth and development of a metazoan organism, we have affinity-purified two SIN3 isoform-specific complexes, SIN3 187 and 220, from Drosophila S2 cells and embryos. We have identified a number of proteins common to the complexes, including the HDAC RPD3, as well as orthologs of several proteins known to have roles in regulating cell proliferation in other organisms. We additionally identified factors, including the histone demethylase little imaginal discs and histone-interacting protein p55, that exhibited a preferential interaction with the largest SIN3 isoform. Our experiments indicate that the isoforms are associated with distinct HDAC activity and are recruited to unique and shared sites along polytene chromosome arms. Furthermore, although expression of SIN3 220 can substitute for genetic loss of other isoforms, expression of SIN3 187 does not support Drosophila viability. Together our findings suggest that SIN3 isoforms serve distinct roles in transcriptional regulation by partnering with different histone-modifying enzymes.
| S-EPMC2930744 | biostudies-literature
Project description:The INDOLE-3-BUTYRIC ACID RESPONSE5 (IBR5) gene encodes a dual specificity phosphatase that regulates plant auxin responses. IBR5 has been predicted to generate two transcripts through alternative splicing, but alternative splicing of IBR5 has not been confirmed experimentally. The previously characterized ibr5-1 null mutant exhibits many auxin related defects such as auxin insensitive primary root growth, defective vascular development, short stature and reduced lateral root development. However, whether all these defects are caused by the lack of phosphatase activity is not clear. Here we describe two new auxin insensitive IBR5 alleles, ibr5-4, a catalytic site mutant, and ibr5-5, a splice site mutant. Characterization of these new mutants indicates that IBR5 is post-transcriptionally regulated to generate two transcripts, AT2G04550.1 and AT2G04550.3, and consequently two IBR5 isoforms, IBR5.1 and IBR5.3. The IBR5.1 isoform exhibits phosphatase catalytic activity that is required for both proper degradation of Aux/IAA proteins and auxin-induced gene expression. These two processes are independently regulated by IBR5.1. Comparison of new mutant alleles with ibr5-1 indicates that all three mutant alleles share many phenotypes. However, each allele also confers distinct defects implicating IBR5 isoform specific functions. Some of these functions are independent of IBR5.1 catalytic activity. Additionally, analysis of these new mutant alleles suggests that IBR5 may link ABP1 and SCF(TIR1/AFBs) auxin signaling pathways.
| S-EPMC4140696 | biostudies-literature
Project description:p53 genes are conserved transcriptional activators that respond to stress. These proteins can also downregulate genes, but the mechanisms are not understood and are generally assumed to be indirect. Here, we investigate synthetic and native cis-regulatory elements in Drosophila to examine opposing features of p53-mediated transcriptional control in vivo. We show that transcriptional repression by p53 operates continuously through canonical DNA binding sites that confer p53-dependent transactivation at earlier developmental stages. p53 transrepression is correlated with local H3K9me3 chromatin marks and occurs without the need for stress or Chk2. In sufficiency tests, two p53 isoforms qualify as transrepressors and a third qualifies as a transcriptional activator. Targeted isoform-specific knockouts dissociate these opposing transcriptional activities, highlighting features that are dispensable for transactivation but critical for repression and for proper germ cell formation. Together, these results demonstrate that certain p53 isoforms function as constitutive tissue-specific repressors, raising important implications for tumor suppression by the human counterpart.
| S-EPMC9378576 | biostudies-literature
Project description:Gamma-tubulin is an indispensable component of the animal centrosome and is required for proper microtubule organization. Within the cell, gamma-tubulin exists in a multiprotein complex containing between two (some yeasts) and six or more (metazoa) additional highly conserved proteins named gamma ring proteins (Grips) or gamma complex proteins (GCPs). gamma-Tubulin containing complexes isolated from Xenopus eggs or Drosophila embryos appear ring-shaped and have therefore been named the gamma-tubulin ring complex (gammaTuRC). Curiously, many organisms (including humans) have two distinct gamma-tubulin genes. In Drosophila, where the two gamma-tubulin isotypes have been studied most extensively, the gamma-tubulin genes are developmentally regulated: the "maternal" gamma-tubulin isotype (named gammaTub37CD according to its location on the genetic map) is expressed in the ovary and is deposited in the egg, where it is thought to orchestrate the meiotic and early embryonic cleavages. The second gamma-tubulin isotype (gammaTub23C) is ubiquitously expressed and persists in most of the cells of the adult fly. In those rare cases where both gamma-tubulins coexist in the same cell, they show distinct subcellular distributions and cell-cycle-dependent changes: gammaTub37CD mainly localizes to the centrosome, where its levels vary only slightly with the cell cycle. In contrast, the level of gammaTub23C at the centrosome increases at the beginning of mitosis, and gammaTub23C also associates with spindle pole microtubules. Here, we show that gammaTub23C forms discrete complexes that closely resemble the complexes formed by gammaTub37CD. Surprisingly, however, gammaTub23C associates with a distinct, longer splice variant of Dgrip84. This may reflect a role for Dgrip84 in regulating the activity and/or the location of the gamma-tubulin complexes formed with gammaTub37CD and gammaTub23C.
| S-EPMC2174168 | biostudies-literature
Project description:BackgroundCAP/Capulet (Capt), Slingshot (Ssh) and Cofilin/Twinstar (Tsr) are actin-binding proteins that restrict actin polymerization. Previously, it was shown that low resolution analyses of loss-of-function mutations in capt, ssh and tsr all show ectopic F-actin accumulation in various Drosophila tissues. In contrast, RNAi depletion of capt, tsr and ssh in Drosophila S2 cells all affect actin-based lamella formation differently. Whether loss of these three related genes might cause the same effect in the same tissue remains unclear.MethodsLoss-of-function mutant clones were generated using the MARCM or EGUF system whereas overexpression clones were generated using the Flip-out system. Immunostaining were then performed in eye imaginal discs with clones. FRAP was performed in cultured eye discs.ResultsHere, we compared their loss-of-function phenotype at single-cell resolution, using a sheet of epithelial cells in the Drosophila eye imaginal disc as a model system. Surprisingly, we found that capt and ssh, but not tsr, mutant cells within and posterior to the morphogenetic furrow (MF) shared similar phenotypes. The capt/ssh mutant cells possessed: (1) hexagonal cell packing with discontinuous adherens junctions; and (2) largely complementary accumulation of excessive phosphorylated myosin light chain (p-MLC) and F-actin rings at the apical cortex. We further showed that the capt/ssh mutant phenotypes depended on the inactivation of protein kinase A (PKA) and activation of Rho.ConclusionsAlthough Capt, Ssh and Tsr were reported to negatively regulate actin polymerization, we found that Capt and Ssh, but not Tsr, share overlapping functions during eye morphogenesis.
| S-EPMC3411472 | biostudies-literature
Project description:The PTPN11 (protein-tyrosine phosphatase, non-receptor type 11) gene encodes SHP2, a cytoplasmic PTP that is essential for vertebrate development. Mutations in PTPN11 are associated with Noonan and LEOPARD syndrome. Human patients with these autosomal dominant disorders display various symptoms, including short stature, craniofacial defects and heart abnormalities. We have used the zebrafish as a model to investigate the role of Shp2 in embryonic development. The zebrafish genome encodes two ptpn11 genes, ptpn11a and ptpn11b. Here, we report that ptpn11a is expressed constitutively and ptpn11b expression is strongly upregulated during development. In addition, the products of both ptpn11 genes, Shp2a and Shp2b, are functional. Target-selected inactivation of ptpn11a and ptpn11b revealed that double homozygous mutants are embryonic lethal at 5-6 days post fertilization (dpf). Ptpn11a-/-ptpn11b-/- embryos showed pleiotropic defects from 4 dpf onwards, including reduced body axis extension and craniofacial defects, which was accompanied by low levels of phosphorylated Erk at 5 dpf. Interestingly, defects in homozygous ptpn11a-/- mutants overlapped with defects in the double mutants albeit they were milder, whereas ptpn11b-/- single mutants did not show detectable developmental defects and were viable and fertile. Ptpn11a-/-ptpn11b-/- mutants were rescued by expression of exogenous ptpn11a and ptpn11b alike, indicating functional redundance of Shp2a and Shp2b. The ptpn11 mutants provide a good basis for further unravelling of the function of Shp2 in vertebrate development.
| S-EPMC3988099 | biostudies-literature
Project description:Irradiated or injured cells enter apoptosis, and in turn, promote proliferation of surrounding unaffected cells. In Drosophila, apoptotic cells have an active role in proliferation, where the caspase Dronc and p53 induce mitogen expression and growth in the surrounding tissues. The Drosophila p53 gene structure is conserved and encodes at least two protein isoforms: a full-length isoform (Dp53) and an N-terminally truncated isoform (DΔNp53). Historically, DΔNp53 was the first p53 isoform identified and was thought to be responsible for all p53 biological activities. It was shown that DΔNp53 induces apoptosis by inducing the expression of IAP antagonists, such as Reaper. Here we investigated the roles of Dp53 and DΔNp53 in apoptosis and apoptosis-induced proliferation. We found that both isoforms were capable of activating apoptosis, but that they each induced distinct IAP antagonists. Expression of DΔNp53 induced Wingless (Wg) expression and enhanced proliferation in both 'undead cells' and in 'genuine' apoptotic cells. In contrast to DΔNp53, Dp53 did not induce Wg expression in the absence of the endogenous p53 gene. Thus, we propose that DΔNp53 is the main isoform that regulates apoptosis-induced proliferation. Understanding the roles of Drosophila p53 isoforms in apoptosis and in apoptosis-induced proliferation may shed new light on the roles of p53 isoforms in humans, with important implications in cancer biology.
| S-EPMC3524635 | biostudies-literature
Project description:A better understanding of the mechanisms underlying obesity and its comorbidities is key to designing new therapies and treatments. PPAR? is a master regulator of adipocyte biology but the functions of its isoforms are poorly distinguished. Here we demonstrated that PPAR?1 is preferentially expressed in catabolic fat depots while PPAR?2 presents itself at a higher level in browning-resistant depots. PPAR?2, but not PPAR?1, responds to endogenous ligands to induce adipogenesis, and the isoforms regulate distinct sets of white and brown adipocyte genes. Moreover, PPAR?1 negatively correlates while PPAR?2 positively correlates with adiposity in human subcutaneous and visceral fat. These results together indicate that PPAR?1 and PPAR?2 have distinct functions in regulating adipocyte plasticity, and future research should take into account the binary roles of both isoforms in order to identify druggable gene targets and pathways relevant for treatment of metabolic disorders.
| S-EPMC5147489 | biostudies-literature
Project description:WNT5A, a member of the WNT family of secreted lipid-modified glycoproteins, is a critical regulator of a host of developmental processes, including limb formation, lung morphogenesis, intestinal elongation and mammary gland development. Altered WNT5A expression has been associated with a number of cancers. Interestingly, in certain types of cancers, such as hematological malignancies and colorectal carcinoma, WNT5A is inactivated and exerts a tumor suppressive function, while in other cancers, such as melanoma and gastric carcinoma, WNT5A is overexpressed and promotes tumor progression. The mechanism by which WNT5A achieves these distinct activities in cancers is poorly understood. Here, we provide evidence that the WNT5A gene produces two protein isoforms, WNT5A-long (WNT5A-L) and WNT5A-short (WNT5A-S). Amino-terminal sequencing and a WNT5A-L specific antibody demonstrate that the mature and secreted isoforms are distinct, with WNT5A-L carrying an additional 18 N-terminal amino acids. Biochemical analysis indicates that both purified proteins are similar with respect to their stability, hydrophobicity and WNT/?-catenin signaling activity. Nonetheless, modulation of these two WNT5A isoforms, either through ectopic expression or knockdown, demonstrates that they exert distinct activities in cancer cell lines: while WNT5A-L inhibits proliferation of tumor cell lines, WNT5A-S promotes their growth. Finally, we show that expression of these two WNT5A isoforms is altered in breast and cervix carcinomas, as well as in the most aggressive neuroblastoma tumors. In these cancers, WNT5A-L is frequently down-regulated, whereas WNT5A-S is found overexpressed in a significant fraction of tumors. Altogether, our study provides evidence that the distinct activities of WNT5A in cancer can be attributed to the production of two WNT5A isoforms.
| S-EPMC3832467 | biostudies-literature
Project description:Deep-sequencing reveals extensive variation in the sequence of endogenously expressed microRNAs (termed 'isomiRs') in human cell lines and tissues, especially in relation to the 3' end. From the immunoprecipitation of the microRNA-binding protein Argonaute and the sequencing of associated small RNAs, we observe extensive 3'-isomiR variation, including for miR-222 where the majority of endogenously expressed miR-222 is extended by 1-5 nt compared to the canonical sequence. We demonstrate this 3' heterogeneity has dramatic implications for the phenotype of miR-222 transfected cells, with longer isoforms promoting apoptosis in a size (but not 3' sequence)-dependent manner. The transfection of longer miR-222 isomiRs did not induce an interferon response, but did downregulate the expression of many components of the pro-survival PI3K-AKT pathway including PIK3R3, a regulatory subunit whose knockdown phenocopied the expression of longer 222 isoforms in terms of apoptosis and the inhibition of other PI3K-AKT genes. As this work demonstrates the capacity for 3' isomiRs to mediate differential functions, we contend more attention needs to be given to 3' variance given the prevalence of this class of isomiR.
| S-EPMC5737821 | biostudies-literature