Biology subjects

Piett, C. G.

Publications and source records attributed to Piett, C. G..

3 recordsLinked to original sources

bioRxiv2024

D-type cyclins regulate DNA mismatch repair in the G1 and S phases of the cell cycle, maintaining genome stability

The large majority of oxidative DNA lesions occurring in the G1 phase of the cell cycle are repaired by base excision repair (BER) rather than mismatch repair (MMR) to avoid long resections that can lead to genomic instability and cell death. However, the molecular mechanisms dictating pathway choice between MMR and BER have remained unknown. Here, we show that, during G1, D-type cyclins are recruited to sites of oxidative DNA damage in a PCNA- and p21-dependent manner. D-type cyclins shield p21 from its two ubiquitin ligases CRL1SKP2 and CRL4CDT2 in a CDK4/6-independent manner. In turn, p21 competes through its PCNA-interacting protein degron with MMR components for their binding to PCNA. This inhibits MMR while not affecting BER. At the G1/S transition, the CRL4AMBRA1-dependent degradation of D-type cyclins renders p21 susceptible to proteolysis. These timely degradation events allow the proper binding of MMR proteins to PCNA, enabling the repair of DNA replication errors. Persistent expression of cyclin D1 during S-phase increases the mutational burden and promotes microsatellite instability. Thus, the expression of D-type cyclins inhibits MMR in G1, whereas their degradation is necessary for proper MMR function in S. One-Sentence SummaryTo maintain genome stability, D-type cyclins limit mismatch repair (MMR) in G1, whereas their degradation is necessary for proper MMR function in S phase.

cell biology↗

bioRxiv2019

Paradoxical role of AT-rich interactive domain 1A in restraining pancreatic carcinogenesis

Background & AimsARID1A is postulated to be a tumor suppressor gene owing to loss-of-function mutations in human pancreatic ductal adenocarcinomas (PDAC). However, its role in pancreatic pathogenesis is not clear despite recent studies using genetically engineered mouse (GEM) models. We aimed at further understanding of its direct functional role in PDAC, using a combination of GEM model, PDAC cell lines. MethodsPancreas-specific mutant Arid1a-driven GEM model (Ptf1a-Cre;KrasG12D;Arid1af/f or "KAC") was generated by crossing Ptf1a-Cre;KrasG12D ("KC") mice with Arid1af/f mice and characterized histologically with timed necropsies. Arid1a was also deleted using CRISPR-Cas9 system in established PDAC cell lines to study the immediate effects of Arid1a loss in isogenic models. Cells lines with or without Arid1a expression were developed from respective autochthonous PDAC GEM models, compared functionally using various culture assays, and subjected to RNA-sequencing for comparative gene expression analysis. DNA damage repair was analyzed in cultured cells using immunofluorescence and COMET assay. ResultsArid1a is critical for early progression of mutant Kras-driven pre-malignant lesions into PDAC, as evident by lower Ki-67 and higher apoptosis staining in "KAC" as compared to "KC" mice. Enforced deletion of Arid1a in established PDAC cell lines caused suppression of cellular growth and migration, accompanied by compromised DNA damage repair. Despite early development of relatively indolent cystic precursor lesions called intraductal papillary mucinous neoplasms (IPMNs), a subset of "KAC" mice developed aggressive PDAC in later ages. PDAC cells obtained from older autochthonous "KAC" mice revealed epigenetic changes underlying the various compensatory mechanisms to overcome the growth suppressive effects of Arid1a loss. ConclusionsArid1a is an essential survival gene whose loss impairs cellular growth, and thus, its expression is critical during early stages of pancreatic tumorigenesis in mouse models.

cancer biology↗

bioRxiv2019

Defective base excision repair in the response to DNA damaging agents in triple negative breast cancer

DNA repair defects have been increasingly focused on as therapeutic targets. In hormone positive breast cancer, XRCC1-deficient tumors have been identified and proposed as targets for combination therapies that damage DNA and inhibit DNA repair pathways. XRCC1 is a scaffold protein that functions in base excision repair (BER) by mediating essential interactions between DNA glycosylases, AP endonuclease, poly(ADP-ribose) polymerase 1, DNA polymerase {beta} (POL {beta}), and DNA ligases. Loss of XRCC1 confers BER defects and hypersensitivity to DNA damaging agents. BER defects have not been evaluated in triple negative breast cancer (TNBC), for which new therapeutic targets and therapies are needed. To evaluate the potential of XRCC1 as an indicator of BER defects in TNBC, we examined XRCC1 expression and localization in the TCGA database and in TNBC cell lines. High XRCC1 expression was observed for TNBC tumors in the TCGA database and expression of XRCC1 varied between TNBC cell lines. We also observed changes in XRCC1 subcellular localization in TNBCs that alter the ability to repair base lesions and single-strand breaks. Subcellular localization changes were also observed for POL {beta} that did not correlate with XRCC1 localization. Basal levels of DNA damage were also measured in the TNBC cell lines, and damage levels correlated with observed changes in XRCC1 expression, localization, and repair functions. The results confirmed that XRCC1 expression changes may indicate DNA repair capacity changes but emphasize that basal DNA damage levels along with expression and localization are better indicators of DNA repair defects. Given the observed over-expression of XRCC1 in TNBC preclinical models and the TCGA database, XRCC1 expression levels should be considered when evaluating treatment responses of TNBC preclinical model cells.

cancer biology↗