SIRT1 negatively regulates the expression of Prl2C3,a senescence-associated protein

SIRT1 is a mammalian homologue of yeast longevity protein Sir2. SIRT1 deacetylates transcription factors, cofactors, and histones in an NAD+-dependent manner, and promotes cell survival, anti-oxidative function, and DNA repair. Although some studies have indicated that SIRT1 is involved in longevity, the function of SIRT1 for preventing aging and senescence is still unclear. In mouse embryonic fibroblasts (MEFs), we found that SIRT1 expression decreased by aging and IRT1 reciprocally regulated the expression level of Prl2C3, one of the prolactin-like peptides. In young MEFs, purified Prl2C3 inhibited the growth and increased the number of senescence-associated β galactosidase-positive cells with enlarged and flattened shapes. Moreover, immunostaining of human skin sections showed the expression of Prl2C3 in the basal cells of the epidermis. These results indicate that SIRT1 negatively regulates a senescence-associated protein rl2C3

CO Multi-line Imaging of Nearby Galaxies (COMING). IX. 12^{12}CO(JJ=2-1)/12^{12}CO(JJ=1-0) line ratio on kiloparsec scales

While molecular gas mass is usually derived from $^{12}$CO($J$=1-0) - the most fundamental line to explore molecular gas - it is often derived from $^{12}$CO($J$=2-1) assuming a constant $^{12}$CO($J$=2-1)/$^{12}$CO($J$=1-0) line ratio ($R_{2/1}$). We present variations of $R_{2/1}$ and effects of the assumption that $R_{2/1}$ is a constant in 24 nearby galaxies using $^{12}$CO data obtained with the Nobeyama 45-m radio telescope and IRAM 30-m telescope. The median of $R_{2/1}$ for all galaxies is 0.61, and the weighted mean of $R_{2/1}$ by $^{12}$CO($J$=1-0) integrated-intensity is 0.66 with a standard deviation of 0.19. The radial variation of $R_{2/1}$ shows that it is high (~0.8) in the inner ~1 kpc while its median in disks is nearly constant at 0.60 when all galaxies are compiled. In the case that the constant $R_{2/1}$ of 0.7 is adopted, we found that the total molecular gas mass derived from $^{12}$CO($J$=2-1) is underestimated/overestimated by ~20%, and at most by 35%. The scatter of a molecular gas surface density within each galaxy becomes larger by ~30%, and at most by 120%. Indices of the spatially resolved Kennicutt-Schmidt relation by $^{12}$CO($J$=2-1) are underestimated by 10-20%, at most 39% in 17 out of 24 galaxies. $R_{2/1}$ has good positive correlations with star-formation rate and infrared color, and a negative correlation with molecular gas depletion time. There is a clear tendency of increasing $R_{2/1}$ with increasing kinetic temperature ($T_{\rm kin}$). Further, we found that not only $T_{\rm kin}$ but also pressure of molecular gas is important to understand variations of $R_{2/1}$. Special considerations should be made when discussing molecular gas mass and molecular gas properties inferred from $^{12}$CO($J$=2-1) instead of $^{12}$CO($J$=1-0).Comment: 29 pages, 18 figures, 5 tables. Accepted for publication in PASJ. The original resolution version is available here (https://astro3.sci.hokudai.ac.jp/~radio/coming/publications/COMING_IX_org_res.pdf