Figure 2. Art27 is a potential transcriptional regulator in cardiac developmental and adult tissues.

(A) Northern blot on RNA derived from eight different heart tissues was probed for expression of GATA-4, FOG-2 and Art27. The membrane was stripped and re-blotted with the appropriate label. The housekeeping gene Gapdh was used as a loading control. Differential binding and/or absence of binding is indicative of probe specificity. (B) P19CL6 embryonal carcinoma cells with stably incorporated GFP under the control of the cardiac Mlc2v promoter [26] were induced to undergo cardiomyocyte differentiation with 1% DMSO. At 5-day increments, mRNA was isolated to assess relative expression of cardiac transcription factors Art27, GATA-4, FOG-2 and Nkx2.5 compared to housekeeping gene Gapdh. These time points correspond to various stages of cardiomyocyte differentiation as determined by systematic scoring of GFP fluorescence and beating intensity. (C) 293a cells were transfected with the various expression plasmids as indicated and GAL₅LEXA₂-Luc reporter activity was assessed. GAL(DBD)-Art27 significantly diminishes reporter activity compared to GAL(DBD)-empty expression plasmid alone showing inherent transcriptional repression activity. GAL(DBD)-SUMO-1 was used as positive control and was observed to repress the activity of the reporter as expected [49] **p<0.01. FH, foetal heart, AH, adult heart, Ao, aorta, Ap, apex, LA, left atrium, RA, right atrium, LV, left ventricle, RV, right ventricle.