SIR2 suppresses replication gaps and genome instability by balancing replication between repetitive and unique sequences.

Replication gaps that persist into mitosis likely represent important threats to genome stability, but experimental identification of these gaps has proved challenging. We have developed a technique that allows us to explore the dynamics by which genome replication is completed before mitosis. Using this approach, we demonstrate that excessive allocation of replication resources to origins within repetitive regions, induced by SIR2 deletion, leads to persistent replication gaps and genome instability. Conversely, the weakening of replication origins in repetitive regions suppresses these gaps. Given known age- and cancer-associated changes in chromatin accessibility at repetitive sequences, we suggest that replication gaps resulting from misallocation of replication resources underlie age- and disease-associated genome instability.

Screen for reactivation of MeCP2 on the inactive X chromosome identifies the BMP/TGF-ß superfamily as a regulator of XIST expression.

Rett syndrome (RS) is a debilitating neurological disorder affecting mostly girls with heterozygous mutations in the gene encoding the methyl-CpG-binding protein MeCP2 on the X chromosome. Because restoration of MeCP2 expression in a mouse model reverses neurologic deficits in adult animals, reactivation of the wild-type copy of MeCP2 on the inactive X chromosome (Xi) presents a therapeutic opportunity in RS. To identify genes involved in MeCP2 silencing, we screened a library of 60,000 shRNAs using a cell line with a MeCP2 reporter on the Xi and found 30 genes clustered in seven functional groups. More than half encoded proteins with known enzymatic activity, and six were members of the bone morphogenetic protein (BMP)/TGF-ß pathway. shRNAs directed against each of these six genes down-regulated X-inactive specific transcript (XIST), a key player in X-chromosome inactivation that encodes an RNA that coats the silent X chromosome, and modulation of regulators of this pathway both in cell culture and in mice demonstrated robust regulation of XIST. Moreover, we show that Rnf12, an X-encoded ubiquitin ligase important for initiation of X-chromosome inactivation and XIST transcription in ES cells, also plays a role in maintenance of the inactive state through regulation of BMP/TGF-ß signaling. Our results identify pharmacologically suitable targets for reactivation of MeCP2 on the Xi and a genetic circuitry that maintains XIST expression and X-chromosome inactivation in differentiated cells.

Effect of Seminar on Compassion on student self-compassion, mindfulness and well-being: A randomized controlled trial.

OBJECTIVE: Mindfulness-based interventions have been shown to have psychological benefits in college students. We explored the effects of an academic Seminar on Compassion on student psychological health. PARTICIPANTS: Forty-one participants (14 male, 27 female, mean age 19.8 ± 1.4 years) were assessed pre- and post- spring semesters 2013 and 2014. METHODS: Students were randomized to the Seminar on Compassion or a wait-list control group. Participants completed self-report measures on anxiety, depression, perceived stress, self-compassion, compassion and mindfulness. Salivary alpha-amylase was also assessed. RESULTS: At baseline, self-compassion and mindfulness were negatively correlated with depression, anxiety, and perceived stress. There were significant changes between the intervention and control group from Time 1 to Time 2 in mindfulness, self-compassion, compassion, and salivary alpha-amylase; however, there were no significant changes in depression, anxiety, and perceived stress. CONCLUSIONS: The course was effective in increasing mindfulness, self-compassion and compassion, and decreasing a salivary marker of stress.