A novel nuclear protein binds centromeric alpha satellite DNA

Abstract

We have previously reported the identification of a naturally occurring junction between alpha satellite and satellite III DNA on human chromosomes 13, 14 and 21 (1). Direct sequence analysis has shown that the 9 bp alphoid-derived direct repeat sequence (GTGAAAAA-G) present at the junction Is fully conserved on these chromosomes. A novel protein, pJα, present in HeLa nuclear extracts, binds to the conserved junction sequence. Mutation analysis of the binding site suggests that pJα can recognize one of the two 9 bp repeats and provides some Insight into nucleotides that are important for binding. Competition studies support the possibility that this protein binds a significant portion of genomlc alpha satellite DNA. Preliminary protein purification experiments have shown that pJα has a molecular weight of 10–15 kDa.