Detection of human satellite II DNA-binding polypeptides in HeLa cellular and nuclear extracts

Highly-repetitive satellite DNA's are generally located in centromeric heterochromatin, yet little is known about how they are maintained and condensed. In an effort to address this question, we have searched for specific satellite DNA-binding proteins in cell-free extracts (both total cellular and nuclear), prepared from HeLa cells, using southwestern blotting. Four polypeptides were detected that specifically bound to a human 1797 bp EcoRI satellite II DNA, which consists in large part of tandemly repeated pentamer (5' TTCCA 3') units, but not to a control probe from plasmid pBR322. These proteins have apparent molecular weights of 100, 93, 77 and 34 kDa and were termed satellite binding protein (Sbp) -1, -2, -3, and -4, respectively.