The adenovirus E1A proteins form complexes with a group of cellular proteins, including a protein of 130 kD. E1A-associated p130 was purified through coimmunoprecipitation with E1A, and sequence data from four tryptic peptides was obtained. Oligonucleotides derived from the peptide sequences were used to clone a 4.85-kb cDNA. The cDNA contained an 1139-amino-acid open reading frame with homology to the retinoblastoma protein and E1A-associated p107 but was more closely related to p107. In vitro-translated p130 bound to E1A, and anti-p130 antibodies detected p130 in immunoblots of E1A immunoprecipitates. p130 was also detected in immunoprecipitates of cyclins A and E and was an efficient substrate in vitro for kinase activities associated with these cyclins. The p130 gene mapped to chromosome 16q12.2-13, a region that undergoes allelic loss in several types of tumors, including hepatocellular, prostate, and breast carcinomas.