Involvement of poly(ADP-ribose)-polymerase in the Pax-6 gene regulation inneuroretina

The quail Pax-6 gene is expressed from two promoters named P0 and P1. P0 pr omoter is under the control of a neuroretina-specific enhancer (EP), This e nhancer activates the P0 promoter specifically in neuroretina cells and in a de developmental stage-dependent manner, The EP enhancer binds efficientl y, as revealed by southwestern experiments, to a 110 kDa protein present in neuroretina cells but not in Quail Embryos Cells and Retinal Pigmented Epi thelium which do not express the P0-initiated mRNAs, To study the role of p 110 in Pax-6 regulation, we have purified the p110 from neuroretina cells e xtracts. Based on the peptide sequence of the purified protein, we have ide ntified the p110 as the poly(ADP-ribose) polymerase (PARP). Using bandshift experiments and footprinting studies, we present evidence that PARP is a c omponent of protein complexes bound to the EP enhancer that increases the o n rate of the protein complex formation to DNA. Using PARP inhibitors (3AB and 6.5 Hphe), we show that these products are able to inhibit EP enhancer activity in neuroretina cells. Finally, we demonstrate that these inhibitor s are able to decrease the expression of the P0-initiated mRNA in the MC29- infected RPE cells which, in contrast to the RPE cells, accumulated the PAR P in response to v-myc expression, Our results suggest that PARP is involve d in the Pax-6 regulation.