DNA mismatch repair (MMR) is a highly conserved pathway that corrects DNA replication errors. Although well characterized, MMR factors remain to be identified. As a 3'-5' exonuclease and endonuclease, meiotic recombination 11 homolog A (MRE11A) is implicated in multiple DNA repair pathways. However, the role of MRE11A in MMR is unclear. Here, we show that MRE11A deficiency increased the sensitivity of HeLa cells to N-methyl-N' nitro-N nitrosoguanidine (MNNG) treatment, implying a potential role of MRE11 in MMR. Moreover, we found MRE11A was largely recruited to chromatin and negatively regulated the DNA damage signals within the first cell cycle after MNNG treatment. We also showed that knockdown of MRE11A increased, while overexpressing MRE11A decreased, MMR activity in HeLa cells, suggesting that MRE11A negatively regulates MMR activity. Furthermore, we show that the recruitment of MRE11A to chromatin requires MLH1 and that MRE11A competes with PMS2 for binding to MLH1. This decreases PMS2 levels in whole cell and on chromatin, and consequently comprises MMR activity. Collectively, our findings reveal that MRE11A is a negative regulator of human MMR.

The cerebellum is implicated in drug addiction. However, the cerebellar neuronal circuitry underlying addiction, especially classic pathway of Purkinje cells (PCs) to deep cerebellar nuclei (DCN), are largely unknown. Here, tracing experiments showed robust projections from the cerebellar lobule VI tyrosine hydroxylase (TH)-positive PCs (PCTH+) to CaMKII-positive glutamatergic neurons in medial cerebellar nucleus (MedCaMKII), forming PCTH+─MedCaMKII pathway. Then, mice were subjected to methylamphetamine (METH)-induced conditioned place preference (CPP), showing that METH exposure excited MedCaMKII and inhibited PCTH+. Silencing MedCaMKII by tettox suppressed the formation and expression of METH-induced CPP, but produced serious motor coordination deficits. Chemogenetic activation of lobule VI PCTH+─Med pathway during METH CPP training blocked the formation and expression of METH-induced CPP without affecting motor coordination, locomotor activity and sucrose reinforcements in mice. Our findings revealed a novel cerebellar lobule VI PCTH+ ─MedCaMKII pathway and pointed out is critical role in encoding METH-preferred behaviors.

No abstract