Fig 6. ssUVR modulation of nuclear HAT and HDAC activities in human keratinocytes.

(A, B) The effect of ssUVR on HAT activity in HaCaT cells (A) and NHEK cells (B). Nuclear fractions from sham and ssUV radiated cells were isolated and histone H3 and H4 specific HAT activities were measured. Data represent the average of three (HaCaT, n = 6) or two (NHEK, n = 4) independent experiments with duplicates. * P<0.05. (C, D) The effect of ssUVR on HDAC activity in HaCaT cells (C) and NHEK cells (D). Nuclear fractions from sham and ssUV radiated cells were isolated and analyzed for HDAC activities. TSA (5 μM) was added to the assay to inhibit class I/II HDAC activities. Data represent the average of two independent experiments with duplicates (n = 4). * P<0.05. (E) The effect of Sirt1 knockdown on ssUVR induced histone hypoacetylation. HaCaT cells were transfected with RNAi oligos against human SIRT1 or control RNAi. 72 hours after transfection, cells were exposed to a single ssUVR at 12 J/cm². Cells were collected at 24 hours after irradiation, and analyzed for Sirt1 and histone acetylation. Antibody against histone H3 was used to access the equal loading of samples in each lane.