Overexpression of mouse p140 subunit of replication factor C accelerates cellular proliferation.

Screening of a murine cDNA expression library with an IFN-stimulated response element (ISRE), as a recognition site DNA probe, resulted in the isolation of a cDNA encoding a polypeptide of 1145 amino acids designated ISRE-binding factor-1. This was subsequently shown to be identical to the M(r) 140,000 subunit of replication factor C (RFC). RFC is required, along with the proliferating cell nuclear antigen and DNA polymerase delta, for the synthesis of the leading strand during DNA replication. RFC exhibits a structure-specific DNA-binding activity that has been localized to its M(r) 140,000 subunit (p140). Sequence-specific binding of this polypeptide to the ISRE occurs only with low affinity. Based on DNA-binding activity of the truncated RFC-p140 encoded by the partial cDNA isolated, the DNA-binding domain of this polypeptide was mapped to a region encoded by amino acids 366 to 540. Transfection of NIH 3T3 cells with an expression plasmid containing murine RFC-p140 driven by cytomegalovirus early promoter led to the establishment of stable cell lines that expressed a 2.5- to 3.0-fold higher RFC-p140 protein level in comparison with control cells. The stable clones exhibited significantly accelerated cell proliferation, indicating that RFC-p140 is the limiting subunit of an active RFC complex in normal cells.