L’évolution des intérêts des adolescents à la fin du collège : 1978-2004

Un questionnaire d’intérêts, le QIm,4,3,2, a été rempli par 482 élèves de classes de troisième en 2004. Les résultats ont été comparés à ceux obtenus en 1978. Il apparaît, d’une part, une baisse des intérêts scientifiques et pour la nature et, d’autre part, une hausse des intérêts pour les relations d’affaires. Quatre catégories d’intérêts paraissent évoluer différemment selon le genre : les intérêts pour le commerce, les intérêts altruistes et les intérêts sportifs augmentent seulement chez les garçons (alors qu’ils sont stables chez les filles) ; à l’inverse, les intérêts artistiques n’augmentent que chez les filles. Ces variations sont cohérentes avec celles qui ont été observées sur des collégiens plus jeunes, elles semblent correspondre à l’évolution sociale générale, mais modifient peu les différences intersexes.An interest inventory, the QIm,4,3,2, has been completed by 482 students of ninth grade in 2004. Results have been compared with those obtained by students in 1978. It discloses a fall in scientific and nature interests and a rise in business interests. Variations differ according to gender in four categories: male students display higher interests than previously in trade, altruism and sports. Female students’ interests appear to be stable in these domains but on the rise in the artistic one (where no change is observed in male students). These variations are consistent with those observed in younger students. They are probably a consequence of a more general social trend. Nevertheless, gender differences in interests remain almost stable

Role of the ubiquitin-binding domain of Polη in Rad18-independent translesion DNA synthesis in human cell extracts

In eukaryotic cells, the Rad6/Rad18-dependent monoubiquitination of the proliferating cell nuclear antigen (PCNA) plays an essential role in the switching between replication and translesion DNA synthesis (TLS). The DNA polymerase Polη binds to PCNA via a consensus C-terminal PCNA-interacting protein (PIP) motif. It also specifically interacts with monoubiquitinated PCNA thanks to a recently identified ubiquitin-binding domain (UBZ). To investigate whether the TLS activity of Polη is always coupled to PCNA monoubiquitination, we monitor the ability of cell-free extracts to perform DNA synthesis across different types of lesions. We observe that a cis-syn cyclobutane thymine dimer (TT-CPD), but not a N-2-acetylaminofluorene-guanine (G-AAF) adduct, is efficiently bypassed in extracts from Rad18-deficient cells, thus demonstrating the existence of a Polη-dependent and Rad18-independent TLS pathway. In addition, by complementing Polη-deficient cells with PIP and UBZ mutants, we show that each of these domains contributes to Polη activity. The finding that the bypass of a CPD lesion in vitro does not require Ub-PCNA but nevertheless depends on the UBZ domain of Polη, reveals that this domain may play a novel role in the TLS process that is not related to the monoubiquitination status of PCNA

Evidence for a Rad18-Independent Frameshift Mutagenesis Pathway in Human Cell-Free Extracts

Bypass of replication blocks by specialized DNA polymerases is crucial for cell survival but may promote mutagenesis and genome instability. To gain insight into mutagenic sub-pathways that coexist in mammalian cells, we examined N-2-acetylaminofluorene (AAF)-induced frameshift mutagenesis by means of SV40-based shuttle vectors containing a single adduct. We found that in mammalian cells, as previously observed in E. coli, modification of the third guanine of two target sequences, 5'-GGG-3' (3G) and 5'-GGCGCC-3' (NarI site), induces –1 and –2 frameshift mutations, respectively. Using an in vitro assay for translesion synthesis, we investigated the biochemical control of these events. We showed that Pol eta, but neither Pol iota nor Pol zeta, plays a major role in the frameshift bypass of the AAF adduct located in the 3G sequence. By complementing PCNA-depleted extracts with either a wild-type or a non-ubiquitinatable form of PCNA, we found that this Pol eta-mediated pathway requires Rad18 and ubiquitination of PCNA. In contrast, when the AAF adduct is located within the NarI site, TLS is only partially dependent upon Pol eta and Rad18, unravelling the existence of alternative pathways that concurrently bypass this lesion

L' ADN polymérase mu (Pol u) (Mise en évidence d'une activité de réplication par translocation en présence d'une lésion AAF et recherche de partenaires)

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Co-localization in replication foci and interaction of human Y-family members, DNA polymerase polη and REVl protein

The progress of replicative DNA polymerases along the replication fork may be impeded by the presence of lesions in the genome. One way to circumvent such hurdles involves the recruitment of specialized DNA polymerases that perform limited incorporation of nucleotides in the vicinity of the damaged site. This process entails DNA polymerase switch between replicative and specialized DNA polymerases. Five eukaryotic proteins can carry out translesion synthesis (TLS) of damaged DNA in vitro, DNA polymerases ¿, ¿, ¿, and ¿, and REV1. To identify novel proteins that interact with hpol¿, we performed a yeast two-hybrid screen. In this paper, we show that hREV1 interacts with hpol¿ as well as with hpol¿ and poorly with hpol¿. Furthermore, cellular localization analysis demonstrates that hREV1 is present, with hpol¿ in replication factories at stalled replication forks and is tightly associated with nuclear structures. This hREV1 nuclear localization occurs independently of the presence of hpol¿. Taken together, our data suggest a central role for hREV1 as a scaffold that recruits DNA polymerases involved in TLS

DNA polymerase η is a substrate for calpain: A possible mechanism for pol η retention in UV induced replication foci

DNA polymerase η (pol η) is specifically required for translesion DNA synthesis across ultraviolet radiation-induced DNA lesions. Recruitment of this error-prone DNA polymerase is tightly regulated during replication to avoid mutagenesis and perturbation of fork progression. Here we report that pol η interacts with the calpain small subunit-1 (CAPNS1), in a yeast two-hybrid screening. This interaction is functional as demonstrated by the ability of endogenous calpain to mediate calcium-dependent cleavage of pol η in cell-free extracts and in living cells treated with a calcium ionophore. The proteolysis of pol η is found to occur at position 465 leading to a catalytically active truncated protein containing the PCNA-interacting motif PIP1. Unexpectedly, cell treatment with the specific calpain inhibitor calpeptin results in a decreased extent of pol η foci after UV irradiation, indicating that calpain positively regulates pol η accumulation in replication foci.</jats:p

Postreplication repair mechanisms in the presence of DNA adducts in Escherichia coli

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