Don't ban genetic engineering.
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Advisory Committees↗
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Results for “Splicing Life”
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Heterogeneous nuclear ribonucleoproteins (hnRNPs): an emerging family of autoantigens in rheumatic diseases.
In eukaryotic cells, mature mRNA molecules are produced through the extensive post-transcriptional processing of primary transcripts assembled in ribonucleoprotein complexes. Twenty polypeptides, termed heterogeneous nuclear ribonucleoproteins or hnRNPs, have been identified as the major components of such complexes. Although these proteins were identified more than 30 years ago, their role in RNA metabolism is just beginning to emerge. In contrast to previous models that ascribed to hnRNPs a mere structural function, recent data suggest a direct involvement in several aspects of the RNA life, such splicing, export of the mature mRNAs to the cell cytoplasm and translation. In addition, a growing body of evidence points to hnRNPs as an important target of the autoimmune response in rheumatic diseases. The present paper will review some of the most relevant data concerning the structure, function and autoantigenic properties of the hnRNPs.
Autoantigens↗
LmxMPK9, a mitogen-activated protein kinase homologue affects flagellar length in Leishmania mexicana.
Components of mitogen-activated signal transduction pathways have been shown to be involved in flagellum biogenesis and maintenance. A mitogen-activated protein kinase homologue, designated LmxMPK9 from Leishmania mexicana, has been recently identified in a homology screen and its mRNA found to be present in all life stages. Three different splice-addition sites were used for mRNA maturation in trans-splicing in the different life stages. However, here we show that LmxMPK9 protein is exclusively found in the promastigote stage. Recombinant expression of LmxMPK9 in Escherichia coli and kinase assays revealed a temperature optimum at 27 degrees C, the optimal growth temperature for L. mexicana promastigotes, and a preference for manganese to promote substrate phosphorylation of myelin basic protein. A deletion mutant for the single-copy gene revealed significantly elongated flagella, whereas overexpression led to a subpopulation with rather short to no flagella suggesting a role for LmxMPK9 in flagellar morphogenesis.
Animals↗
High frequency of alternative splicing of human genes participating in the HIV-1 life cycle: a model using TSG101, betaTrCP, PPIA, INI1, NAF1, and PML.
Alternative splicing may generate splice forms with different biologic roles or missing protein domains implicated in the interaction with HIV-1. To address this issue, 6 human genes were investigated-tumor suppressor gene 101 (TSG101), beta-transducin repeats containing protein (betaTrCP), peptidyl-proly cis-trans isomerase, cyclophilin A (PPIA), integrase interactor 1 protein (INI1), Nef-associated factor 1 (NAF1), and promyelacytic leukemia (PML)-involved in the viral life cycle and HIV-1 pathogenesis. All 6 genes presented alternative splicing, and a combined bioinformatic and reverse transcription polymerase chain reaction (RT-PCR) analysis identified 27 new variants for a total of 53 splice forms (an average of 9 variants per gene). The predicted frequency of the various splice forms based on expressed sequence tags (EST) analysis corresponded to the semiquantitative findings on RT-PCR analysis for the cell culture systems and for native CD4 cells investigated. Interindividual variation in the frequencies of various splice forms in CD4 T cells from blood donors was observed for INI1. Cell type-specific variation of splice pattern was observed for NAF1. Eight splice forms lacked or modified motifs implicated in the interaction with HIV-1, underscoring the potential interest of assessing alternative splicing when investigating viral cell biology and pathogenesis.
Alternative Splicing↗
Stage-specific alternative splicing of the heat-shock transcription factor during the life-cycle of Schistosoma mansoni.
Stage-specific alternative splicing of the heat-shock transcription factor of Schistosoma mansoni (SmHSF) generates isoforms with structural diversity that may modulate the activity of SmHSF at different life-stages, and thus may regulate the expression of different genes at different developmental stages. RT-PCR, cloning and DNA-sequence analyses showed stage-specific alternative splicing inside the DNA-binding domain (DBD) involving introns I1 and I2, and beyond the DBD involving introns I4a and I7. Retention of introns I2 and I4 would inactivate SmHSF since they contain termination codons. Retention of intron I1 would add 11 amino acids inside the DBD and may change the DNA-binding specificity of SmHSF; intron I7 would add 13 amino acids to the effector region of HSF. Retention of introns was more pronounced in cercariae (larval stage living in water) than in adult worms (parasitic form in mammals). The isoforms were expressed in bacteria, but functional evaluation was not feasible, because only the isoform lacking introns was soluble while isoforms with introns were insoluble. However, stage-specific alternative splicing that changed HSF function in vivo was evidenced in intact cercariae. The cercarial SmHSF mRNA was enriched with introns I2 and I4a that contain termination codons. Therefore, translation of the SmHSF mRNA was impaired, and the SmHSF protein was undetectable. Consequently, the HSP70 gene could not be transcribed, and the HSP70 mRNA was missing. Alternative splicing was observed for short DNA segments (33-45 bp) bound by splice signals, located in the coding region. These are not bona fida exons since they are not flanked by introns. Yet, they are not regular introns since they are often found in mature mRNA. Alternative splicing of these DNA segments caused structural diversity that could modulate the function of the gene product.
Alternative Splicing↗
Pre-mRNA trans-splicing: from kinetoplastids to mammals, an easy language for life diversity.
Since the discovery that genes are split into intron and exons, the studies of the mechanisms involved in splicing pointed to presence of consensus signals in an attempt to generalize the process for all living cells. However, as discussed in the present review, splicing is a theme full of variations. The trans-splicing of pre-mRNAs, the joining of exons from distinct transcripts, is one of these variations with broad distribution in the phylogenetic tree. The biological meaning of this phenomenon is discussed encompassing reactions resembling a possible noise to mechanisms of gene expression regulation. All of them however, can contribute to the generation of life diversity.
Animals↗
Evidence that the decay of nucleus-associated nonsense mRNA for human triosephosphate isomerase involves nonsense codon recognition after splicing.
For most of the mammalian mRNAs that have been shown to be reduced in abundance by a nonsense or a frameshift mutation that generates a nonsense codon, reduction takes place while the mRNA is nucleus-associated rather than after the mRNA has been exported to the cytoplasm (reviewed in Maquat LE, 1995, RNA 1:453-465). A variety of mechanisms have been put forth to explain how a nonsense codon could affect the abundance of nuclear mRNA. Some mechanisms have implicated nonsense codon recognition in the nucleus prior to splicing. Among the best-studied nonsense transcripts that manifest nonsense-mediated alterations in nucleus-associated metabolism are those that derive from human alleles for the glycolytic enzyme triosephosphate isomerase (TPI). Nonsense codons within TPI transcripts have been shown to reduce the half-life of completely spliced TPI (mRNA that co-purifies with nuclei (Belgrader P et al., 1994, Mol Cell Biol 14:8219-8228). However, whether or not nonsense codon recognition within TPI transcripts takes place prior to or after splicing remained unresolved. To address this issue, codons that span two exons, i.e., are disrupted by an intron prior to pre-mRNA splicing, were converted to nonsense. If nonsense codon recognition were to precede splicing, then the disrupting intron would be expected to preclude nonsense codon recognition by preventing the physical juxtapositioning of the codon nucleotides. In the absence of nonsense codon recognition, there would be no nonsense-mediated reduction in TPI mRNA abundance. The results of northern (RNA) blot hybridization demonstrated that the two nonsense codons of this type that were studied reduced the level of total, nuclear and cytoplasmic TPI mRNA to an average of 12% of normal, consistent with each nonsense codon being competent to mediate nuclear mRNA degradation. The possibility that the nonsense codons reduced TPI mRNA abundance by altering TPI mRNA abundance or splicing was eliminated by using RT-PCR to demonstrate that the level of each intron within pre-mRNA was essentially unaffected and cDNA sequencing to demonstrate that splice site choice was unaltered. Furthermore, missense codons that harbored some of the nonsense codon changes were found to have little effect on mRNA abundance. These findings, plus the previous finding that a suppressor tRNA abrogates the decay of TPI mRNA brought about by a nonsense codon residing within a single exon (Belgrader P, Cheng J, Maquat LE, 1993, Proc Natl Acad Sci USA 90:482-486), argue strongly that nonsense codon recognition in the nonsense-mediated decay of TPI mRNA takes place after splicing.
Base Sequence↗
Different protein turnover of interleukin-6-type cytokine signalling components.
Interleukin (IL)-6 and IL-6-type cytokines signal through the gp130/Jak/STAT signal transduction pathway. The key components involved are the signal transducing receptor subunit gp130, the Janus kinases Jak1, Jak2 and Tyk2, STAT1 and STAT3 of the family of signal transducers and activators of transcription, the protein tyrosine phosphatase SHP2 and the suppressors of cytokine signalling SOCS1, SOCS2 and SOCS3. Whereas considerable information has been accumulated concerning the time-course of activation for the individual signalling molecules, data on the availability of the proteins involved in IL-6-type cytokine signal transduction are scarce. Nevertheless, availability of these molecules, determined by the balance of protein synthesis and degradation, also influences IL-6-type cytokine signal transduction. Here, we present a comprehensive set of data on the half-lives of the key molecules involved in the IL-6 signal transduction pathway. The turnover rates for the various proteins differ substantially. Three groups of signalling proteins can be discriminated: whereas the feedback inhibitors SOCS1, SOCS2 and SOCS3 are very short-lived, STAT1, STAT3 and SHP2 have an extremely slow turnover rate. Interestingly, the half-life of STAT3beta, a splice variant of STAT3alpha, is reduced to almost 50% of the half-life of STAT3alpha. The Janus kinases Jak1, Jak2, Tyk2 and gp130 show intermediate half-lives. Our data imply that signalling components activated by post-translational modifications are long-lived whereas the activity of very short-lived proteins is regulated mainly at the transcriptional level.
Antigens, CD↗
Shaping life in the lab--and profiting from gene splicing.
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Conflict of Interest↗
Selection of the bovine papillomavirus type 1 nucleotide 3225 3' splice site is regulated through an exonic splicing enhancer and its juxtaposed exonic splicing suppressor.
Alternative splicing is an important mechanism for the regulation of bovine papillomavirus type 1 (BPV-1) gene expression during the virus life cycle. However, one 3' splice site, located at nucleotide (nt) 3225, is used for the processing of most BPV-1 pre-mRNAs in BPV-1-transformed C127 cells and at early to intermediate times in productively infected warts. At late stages of the viral life cycle, an alternative 3' splice site at nt 3605 is used for the processing of the late pre-mRNA. In this study, we used in vitro splicing in HeLa cell nuclear extracts to identify cis elements which regulate BPV-1 3' splice site selection. Two purine-rich exonic splicing enhancers were identified downstream of nt 3225. These sequences, designated SE1 (nt 3256 to 3305) and SE2 (nt 3477 to 3526), were shown to strongly stimulate the splicing of a chimeric Drosophila doublesex pre-mRNA, which contains a weak 3' splice site. A BPV-1 late pre-mRNA containing the nt 3225 3' splice site but lacking both SE1 and SE2 was spliced poorly, indicating that this 3' splice site is inherently weak. Analysis of the 3' splice site suggested that this feature is due to both a nonconsensus branch point sequence and a suboptimal polypyrimidine tract. Addition of SE1 to the late pre-mRNA dramatically stimulated splicing, indicating that SE1 also functions as an exonic splicing enhancer in its normal context. However, a late pre-mRNA containing both SE1 and SE2 as well as the sequence in between was spliced inefficiently. Further mapping studies demonstrated that a 48-nt pyrimidine-rich region immediately downstream of SE1 was responsible for this suppression of splicing. Thus, these data suggest that selection of the BPV-1 nt 3225 3' splice site is regulated by both positive and negative exonic sequences.
Animals↗
Regulation of insulin preRNA splicing by glucose.
Glucose tightly regulates the synthesis and secretion of insulin by beta cells in the pancreatic islets of Langerhans. To investigate whether glucose regulates insulin synthesis at the level of insulin RNA splicing, we developed a method to detect and quantify a small amount of RNA by using the branched DNA (bDNA) signal-amplification technique. This assay is both sensitive and highly specific: mouse insulin II mRNA can be detected from a single beta cell (betaTC3 cells or mouse islets), whereas 1 million non-insulin-producing alpha cells (alphaTC1.6 cells) give no signal. By using intron and exon sequences, oligonucleotide probes were designed to distinguish the various unspliced and partially spliced insulin preRNAs from mature insulin mRNA. Insulin RNA splicing rates were estimated from the rate of disappearance of insulin preRNA signal from beta cells treated with actinomycin D to block transcription. We found that the two introns in mouse insulin II are not spliced with the same efficiency. Intron 2 is spliced out more efficiently than intron 1. As a result, some mRNA retaining intron 1 enters the cytoplasm, making up approximately 2-10% of insulin mRNA in the cell. This partially spliced cytoplasmic mRNA is quite stable, with a half-life similar to the completely spliced form. When islets grown in high glucose are shifted to low glucose medium, the level of insulin preRNA and the rate of splicing fall significantly. We conclude that glucose stimulates insulin gene transcription and insulin preRNA splicing. Previous estimates of insulin transcription rates based on insulin preRNA levels that did not consider the rate of splicing may have underestimated the effect of glucose on insulin gene transcription.
Animals↗
The mRNA structure has potent regulatory effects on type 2 iodothyronine deiodinase expression.
Type 2 deiodinase (D2) is a selenoenzyme catalyzing the activation of T(4) to T(3). D2 activity/mRNA ratios are often low, suggesting that there is significant posttranscriptional regulation. The D2 mRNA in higher vertebrates is more than 6 kb, containing long 5' and 3' untranslated regions (UTRs). The D2 5'UTRs are greater than 600 nucleotides and contain 3-5 short open reading frames. These full-length 5'UTRs reduce the D2 translation efficiency approximately 5-fold. The inhibition by human D2 5'UTR is localized to a region containing the first short open reading frame encoding a tripeptide-MKG. This inhibition was abolished by mutating the AUG start codon and weakened by modification of the essential purine of the Kozak consensus. Deletion of the 3.7-kb 3'UTR of the chicken D2 mRNA increased D2 activity approximately 3.8-fold due to an increase in D2 mRNA half-life. In addition, alternatively spliced D2 mRNA transcripts similar in size to the major 6- to 7-kb D2 mRNAs but not encoding an active enzyme are present in both human and chicken tissues. Our results indicate that a number of factors reduce the D2 protein levels. These mechanisms, together with the short half-life of the protein, ensure limited expression of this key regulator of T(4) activation.
3' Untranslated Regions↗
Optional exon in the 5'-untranslated region of 3-hydroxy-3-methylglutaryl coenzyme A synthase gene: conserved sequence and splicing pattern in humans and hamsters.
3-Hydroxy-3-methylglutaryl coenzyme A synthase (hydroxymethylglutaryl-CoA synthase, EC 4.1.3.5) is a negatively regulated enzyme in the synthetic pathway for cholesterol, isopentenyl tRNA, and other isoprenoids. The 5'-untranslated region of the mRNA for Chinese hamster hydroxymethylglutaryl-CoA synthase contains an optional exon of 59 nucleotides located 10 nucleotides upstream of the translation start site. About 50% of the mRNAs contain this exon, and the other 50% lack it owing to differential intron splicing. We show that the two transcripts are found in similar ratios in multiple tissues of the Syrian hamster, including the brain. The relative amounts of the two transcripts in brain and liver are constant from day 0 to day 75 of life. A similar alternative splicing pattern for hydroxymethylglutaryl-CoA synthase was observed in three human tissues: cultured fibroblasts, fetal adrenal gland, and fetal liver. A cDNA for human synthase had 90% homology to the hamster sequence in the region corresponding to the optional exon. This sequence contains a 20 out of 26 nucleotide match with the sequence immediately upstream of the initiator AUG codon in the mRNA for hamster hydroxymethylglutaryl-CoA reductase, the enzyme that follows the synthase in the isoprenoid biosynthetic pathway. These findings raise the possibility that the optional exon plays an important, conserved functional role in humans and hamsters.
Aging↗
Inteins, introns, and homing endonucleases: recent revelations about the life cycle of parasitic genetic elements.
Self splicing introns and inteins that rely on a homing endonuclease for propagation are parasitic genetic elements. Their life-cycle and evolutionary fate has been described through the homing cycle. According to this model the homing endonuclease is selected for function only during the spreading phase of the parasite. This phase ends when the parasitic element is fixed in the population. Upon fixation the homing endonuclease is no longer under selection, and its activity is lost through random processes. Recent analyses of these parasitic elements with functional homing endonucleases suggest that this model in its most simple form is not always applicable. Apparently, functioning homing endonuclease can persist over long evolutionary times in populations and species that are thought to be asexual or nearly asexual. Here we review these recent findings and discuss their implications. Reasons for the long-term persistence of a functional homing endonuclease include: More recombination (sexual and as a result of gene transfer) than previously assumed for these organisms; complex population structures that prevent the element from being fixed; a balance between active spreading of the homing endonuclease and a decrease in fitness caused by the parasite in the host organism; or a function of the homing endonuclease that increases the fitness of the host organism and results in purifying selection for the homing endonuclease activity, even after fixation in a local population. In the future, more detailed studies of the population dynamics of the activity and regulation of homing endonucleases are needed to decide between these possibilities, and to determine their relative contributions to the long term survival of parasitic genes within a population. Two outstanding publications on the amoeba Naegleria group I intron (Wikmark et al. BMC Evol Biol 2006, 6:39) and the PRP8 inteins in ascomycetes (Butler et al.BMC Evol Biol 2006, 6:42) provide important stepping stones towards integrated studies on how these parasitic elements evolve through time together with, or despite, their hosts.
Amoeba↗
Intronic sequences and 3' splice sites control Rous sarcoma virus RNA splicing.
cis-acting sequences of Rous sarcoma virus (RSV) RNA involved in control of the incomplete splicing that is part of the retroviral life cycle have been studied. The 5' and two alternative 3' splice sites, as well as negative regulator of splicing element in the intron, have been introduced into chimeric constructs, and their responsive roles in splicing inhibition have been evaluated by transient transfection experiments. Although the RSV 5' splice site was used efficiently in these assays, substrates containing either the RSV env or the RSV src 3' splice site were not spliced completely, resulting in 40 to 50% unspliced RNA. Addition of the negative regulator of splicing element to substrates containing RSV 3' splice sites resulted in greater inhibition of splicing (70 to 80% unspliced RNA), suggesting that the two elements function independently and additively. Deletion of sequences more than 70 nucleotides upstream of the src 3' splice site resulted in efficient splicing at this site, suggesting that inefficient usage is not inherent in this splice site but is instead due to to sequences upstream of it. Insertion of these upstream sequences into the intron of a heterologous pre-mRNA resulted in partial inhibition of its splicing. In addition, secondary structure interactions were predicted to occur between the src 3' splice site and the inhibitory sequences upstream of it. Thus, RSV splicing control involves both intronic sequences and 3' splice sites, with different mechanisms involved in the underutilization of the env and src splice acceptor sites.
Avian Sarcoma Viruses↗
Patterns of developmental expression of the RNA editing enzyme rADAR2.
To date, two structurally related RNA-editing enzymes with adenosine deaminase activity have been identified in mammalian tissue: ADAR1 and ADAR2 [Bass B. I. et al. (1997) RNA 3, 947-949]. In rodents, ADAR2 undergoes alternative RNA splicing, giving rise to two splice variants that differ by the presence or absence of a 10-amino-acid insert in the carboxy-terminal catalytic domain. However, the physiological significance of the splicing and its regional and developmental regulation are as yet unknown. The present study examined spatial and temporal patterns of ADAR2 gene transcripts within specific neuronal populations of rat brain. The two rodent ADAR2 isoforms were expressed at comparable levels at all ages examined. rADAR2 messenger RNA expression was first detectable in the thalamic nuclei formation at embryonic day E19. The rADAR2b insert and rADAR2a splice probes produced images similar to that of the rADAR2 pan probe. At birth, rADAR2a messenger RNA splice variants were abundantly expressed in the thalamic nuclei. No signal for any probe was detectable in other brain regions, including neocortex, hippocampus, striatum and cerebellum at this stage of development. During the first week of postnatal life, rADAR2 messenger RNA expression (detected with the pan probe) increased gradually in several brain regions, with low expression detected at postnatal day P7 in the olfactory bulb, inferior colliculus, and within the pyramidal and granule cell layers of the hippocampus. Hybridization patterns of the rADAR2a variant probe reached peak expression at about the second week of life, while peak expression of the rADAR2b probe was reached at about the third week of life. At the end of the first week of life (P7), expression of both splice variants was strongest in the thalamic nuclei. By P14, rADAR2 messenger RNA expression was more consolidated in the deeper structures, including the thalamic nuclei and the granule cell layer of the cerebellum. By P21, maximal levels of rADARb expression were observed in the thalamic nuclei, inferior colliculus, cerebellum and pontine nuclei. In the adult, rADAR2 messenger RNA expression was of highest intensity in the thalamic nuclei, with high levels of expression in the olfactory bulb, inferior colliculus, cerebellum and pontine nuclei. At the level of the hippocampus, positive labelling was restricted to the CA3 region of the Ammon's horn and the dentate gyrus, with weak signals in the CA1 subfield. rADAR2 pan expression was at near background levels throughout the neocortex and caudate putamen. In summary, our study shows that ADAR2 messenger RNA expression is regulated in a cell-specific manner throughout development. At early ages, ADAR2 messenger RNA is expressed only within (and restricted to) the thalamic nuclei. By the third postnatal week, expression of the editase enzyme is more widely distributed throughout the olfactory bulb, CA3 and dentate gyrus of the hippocampus, thalamus, inferior colliculus and the molecular cell layer of the cerebellum. ADAR2 is thought to act at specific nucleotide positions in primary transcripts encoding glutamate receptor subunits, thereby altering gating and ionic permeability properties of AMPA- and kainate-activated channels. ADAR2 also acts at pre-messenger RNA encoding the serotonin 5HT-2C receptor to alter G-protein coupling. Thus, RNA editing may be an important mechanism for fine-tuning of the physiological and pharmacological properties of transmitter receptors of the central nervous system.
Adenosine Deaminase↗
Poly(ADP-ribose) polymerase-1 regulates the stability of the wild-type p53 protein.
We investigated the interaction between poly(ADP-ribose) polymerase-1 (PARP-1) and the product of the tumor suppressor gene p53 using two different approaches. In the first approach, we used primary and immortalized cells derived from wt and PARP-1 -/- mice. We examined whether PARP-1 deficiency would affect the expression of the wild-type (wt) p53 protein. The inactivation of the PARP-1 gene markedly affected the constitutive expression of the wt p53 protein. Interestingly, only the regularly spliced form of wt p53 was reduced to a barely detectable level in consequence to an approximately 8-fold shortening of its half-life, whereas the level of alternatively spliced p53 remained unchanged. Moreover, reconstitution of cells lacking the PARP-1 gene with the human counterpart restored the normal stability of the regularly spliced p53 protein. In the second approach, we performed experiments with c-Ha-ras transformed primary rat cells overexpressing the p53135val mutant alone or in combination with PARP-1. The advantage of this temperature sensitive p53135val mutant is its oncogenic character at 37 degrees C, connected with cytoplasmic localization of p53, and its tumor suppressor activity at 32 degrees C, accompanied by p53 translocation into the nucleus. No noticeable differences in proliferation and G1 accumulationwere observed between cells expressing p53135val with or without PARP-1. On the other hand, a comparison of the recovery of G1 arrested cells after a shift up to 37 degrees C for both cell lines showed dramatic differences in the kinetics. While cells expressing p53135val rapidly reached the characteristic S-phase level after a shift up to basal temperature, cells additionally expressing PARP-1 rested in G1 despite the temperature elevation. This coincided with exclusively cytoplasmic p53 protein in cells expressing p53135val and predominantly nuclear localization of p53 in p53135val +PARP-1 cells, as evidenced by immunostaining. Determination of the p53 level during the maintenance of cells at 32 degrees C revealed a marked decrease in the level of p53 in cells expressing p53135val alone, whereas in cells coexpressing PARP-1, the level of p53 remained largely unaffected. This indicates that the stability of wild-type p53 greatly differed between both cell lines. Furthermore, the inhibition of PARP-1 activity in G1 arrested cells by 3-aminobenzamide abolished its stabilizing effect on the wild-type p53 protein. Taken together, our results indicate that PARP-1 regulates the stability of the wt p53 protein and that its enzymatic activity is necessary for this stabilizing action.
Alternative Splicing↗
The p66shc adaptor protein controls oxidative stress response and life span in mammals.
Gene mutations in invertebrates have been identified that extend life span and enhance resistance to environmental stresses such as ultraviolet light or reactive oxygen species. In mammals, the mechanisms that regulate stress response are poorly understood and no genes are known to increase individual life span. Here we report that targeted mutation of the mouse p66shc gene induces stress resistance and prolongs life span. p66shc is a splice variant of p52shc/p46shc (ref. 2), a cytoplasmic signal transducer involved in the transmission of mitogenic signals from activated receptors to Ras. We show that: (1) p66shc is serine phosphorylated upon treatment with hydrogen peroxide (H2O2) or irradiation with ultraviolet light; (2) ablation of p66shc enhances cellular resistance to apoptosis induced by H2O2 or ultraviolet light; (3) a serine-phosphorylation defective mutant of p66shc cannot restore the normal stress response in p66shc-/- cells; (4) the p53 and p21 stress response is impaired in p66shc-/- cells; (5) p66shc-/- mice have increased resistance to paraquat and a 30% increase in life span. We propose that p66shc is part of a signal transduction pathway that regulates stress apoptotic responses and life span in mammals.
Adaptor Proteins, Signal Transducing↗