Ataxia-telangiectasia mutated and Rad3 related (ATR)-Seckel syndrome and autosomal recessive primary microcephaly (MCPH) syndrome share clinical features. RNA interference (RNAi) of MCPH1 have implicated the protein it encodes as a DNA-damage response protein that regulates the transcription of Chk1 and BRCA1, two genes involved in the response to DNA damage. Here, we report that truncating mutations observed in MCPH-syndrome patients do not impact on Chk1 or BRCA1 expression or early ATR-dependent damage-induced phosphorylation events. However, like ATR-Seckel syndrome cells, MCPH1-mutant cell lines show defective G2-M checkpoint arrest and nuclear fragmentation after DNA damage, and contain supernumerary mitotic centrosomes. MCPH1-mutant and ATR-Seckel cells also show impaired degradation of Cdc25A and fail to inhibit Cdc45 loading onto chromatin after replication arrest. Additionally, microcephalin interacts with Chk1. We conclude that MCPH1 has a function downstream of Chk1 in the ATR-signalling pathway. In contrast with ATR-Seckel syndrome cells, MCPH1-mutant cells have low levels of Tyr 15-phosphorylated Cdk1 (pY15-Cdk1) in S and G2 phases, which correlates with an elevated frequency of G2-like cells displaying premature chromosome condensation (PCC). Thus, MCPH1 also has an ATR-independent role in maintaining inhibitory Cdk1 phosphorylation, which prevents premature entry into mitosis.

No abstract

Objectives Despite growing evidence of the impact of smoking on diabetes complications, people with type 2 diabetes still smoke at high rates and little is known about the specific barriers to quit smoking in this group. The purpose of this article is to explore the perception of smoking, and motivation and barriers to quit among smokers with type 2 diabetes. This exploratory study will help designing a smoking cessation intervention tailored to the needs of people with type 2 diabetes. We hypothesize both that living with diabetes and gender may raise additional difficulties to quit smoking. Setting The qualitative exploratory research included ten in-depth semi-structured individual interviews and five focus groups conducted in an Ambulatory Care University Hospital in Switzerland. The thematic analysis was conducted with a gender-sensitive focus. Participants Both current and former smokers recruited from the ambulatory clinic and the community took part in the qualitative interviews. We restricted the analysis to 21 current smokers only. Results The sample included 12 men and 9 women with type 2 diabetes, having a mean age of 59.4 years, who had diabetes for an average of 9 years with a mean HbA1c of 7.4%. We found that harmful effects of tobacco were superficially understood, and participants used several patterns of thinking to minimize the risks. The relation between tobacco and diabetes was poorly known. Readiness to change was related to personal self-image and meaningful engagement in life and social relationships. Barriers could be organized into three groups: dependence, psychological habits and social barriers. Barriers were markedly shaped by gender and living with diabetes. Conclusions Results suggest that “one -fits-all” smoking cessation interventions do not satisfy the needs of type 2 diabetic smokers. Personalized smoking cessation interventions should be preferred and should pursue positive psychological outcomes addressing contextual factors.

BackgroundThe retinoblastoma protein (Rb) is a crucial regulator of cell cycle progression by binding with E2F transcription factor and repressing the expression of a variety of genes required for the G1-S phase transition.Methodology/Principal FindingsHere we show that Rb and E2F1 directly participate in the control of initiation of DNA replication in human HeLa, U2OS and T98G cells by specifically binding to origins of DNA replication in a cell cycle regulated manner. We show that, both in vitro and inside the cells, the largest subunit of the origin recognition complex (Orc1) specifically binds hypo-phosphorylated Rb and that this interaction is competitive with the binding of Rb to E2F1. The displacement of Rb-bound Orc1 by E2F1 at origins of DNA replication marks the progression of the G1 phase of the cell cycle toward the G1-S border.Conclusions/SignificanceThe participation of Rb and E2F1 in the formation of the multiprotein complex that binds origins of DNA replication in mammalian cells appears to represent an effective mechanism to couple the expression of genes required for cell cycle progression to the activation of DNA replication.