Polymerase Delta Interacting Protein 1 (POLdIP1)

KCTD13 encodes a predicted 329-amino acid protein of 36.4 kD molecular mass, and shows 62% amino acid identity with B12 (TNFAIP1), a TNF early-response gene. Northern blot analysis showed ubiquitous expression of a 1.8-kb KCTD13 transcript, with highest expression levels in liver and kidney.

KCTD13 is a nuclear protein that colocalizes with PCNA at replication foci. KCTD13 binds to POLD2 and to PCNA in vitro, and GST pull-down assays demonstrated that KCTD13 binds these 2 proteins simultaneously. KCTD13 stimulates the polymerase activity of POLD2 when PCNA is present. Similar to that of TNFAIP1, KCTD13 expression is induced by TNF-alpha and by IL6.