Phosphorylation Alters the Properties of Pol η: Implications for Translesion Synthesis.

There are significant ambiguities regarding how DNA polymerase η is recruited to DNA lesion sites in stressed cells while avoiding normal replication forks in non-stressed cells. Even less is known about the mechanisms responsible for Pol η-induced mutations in cancer genomes. We show that there are two safeguards to prevent Pol η from adventitious participation in normal DNA replication. These include sequestration by a partner protein and low basal activity. Upon cellular UV irradiation, phosphorylation enables Pol η to be released from sequestration by PDIP38 and activates its polymerase function through increased affinity toward monoubiquitinated proliferating cell nuclear antigen (Ub-PCNA). Moreover, the high-affinity binding of phosphorylated Pol η to Ub-PCNA limits its subsequent displacement by Pol δ. Consequently, activated Pol η replicates DNA beyond the lesion site and potentially introduces clusters of mutations due to its low fidelity. This mechanism could account for the prevalence of Pol η signatures in cancer genome.

Regulation of nonclassical renin-angiotensin system receptor gene expression in the adrenal medulla by acute and repeated immobilization stress.

The involvement of the nonclassical renin-angiotensin system (RAS) in the adrenomedullary response to stress is unclear. Therefore, we examined basal and immobilization stress (IMO)-triggered changes in gene expression of the classical and nonclassical RAS receptors in the rat adrenal medulla, specifically the angiotensin II type 2 (AT2) and type 4 (AT4) receptors, (pro)renin receptor [(P)RR], and Mas receptor (MasR). All RAS receptors were identified, with AT2 receptor mRNA levels being the most abundant, followed by the (P)RR, AT1A receptor, AT4 receptor, and MasR. Following a single IMO, AT2 and AT4 receptor mRNA levels decreased by 90 and 50%, respectively. Their mRNA levels were also transiently decreased by repeated IMO. MasR mRNA levels displayed a 75% transient decrease as well. Conversely, (P)RR mRNA levels were increased by 50% following single or repeated IMO. Because of its abundance, the function of the (P)RR was explored in PC-12 cells. Prorenin activation of the (P)RR increased phosphorylation of extracellular signal-regulated kinase 1/2 and tyrosine hydroxylase at Ser(31), likely increasing its enzymatic activity and catecholamine biosynthesis. Together, the broad and dynamic changes in gene expression of the nonclassical RAS receptors implicate their role in the intricate response of the adrenomedullary catecholaminergic system to stress.

Comparative effects of intranasal neuropeptide Y and HS014 in preventing anxiety and depressive-like behavior elicited by single prolonged stress.

Stress triggered neuropsychiatric disorders are a serious societal problem. Prophylactic treatment or early intervention has great potential in increasing resilience to traumatic stress and reducing its harmful impact. Previously, we demonstrated proof of concept that intranasal administration of neuropeptide Y (NPY) or the melanocortin receptor four (MC4R) antagonist, HS014, prior to single prolonged stress (SPS) rodent post-traumatic stress disorder (PTSD) model, can prevent or attenuate many PTSD associated impairments. Here, we compare effects of NPY or HS014 given 30 min before or immediately after SPS stressors on development of anxiety, depressive-like behavior and associated biochemical abnormalities. SPS triggered anxiety on elevated plus maze (EPM) was reduced by intranasal administration of 100 µg NPY and to even greater extent HS014 (3.5 ng or 100 µg). The SPS-elicited depressive-like behavior on forced swim test was prevented with 100 µg NPY or the high dose HS014. Combined administration of low HS014 and NPY, ineffective by themselves, prevented development of depressive-like behavior. Reductions in stress triggered activation of locus coeruleus/noradrenergic system and HPA axis were observed with both HS014 and NPY. In contrast to NPY which has been showed earlier, infusion of HS014 immediately after SPS did not prevent the development of anxiogenic behavior on EPM. However, HS014 given after SPS stressors effectively even at very low dose, prevented development of depressive-like behavior. Thus, both MC4R antagonist and NPY, alone or combined, have potential for prophylactic treatment against traumatic stress triggered anxiety or depressive-like behaviors, while NPY has more widespread potential for early intervention.