Isolation And Functional Analysis Of Rat PDIP1β Gene

Tumor necrosis factor (TNF- ) is a multifunctional cytokine that plays roles in a variety of cellular processes, such as apoptosis, proliferation, B cell activation, liver regeneration and some inflammatory responses. Human polymerase delta-interacting protein 1 (PDIP1) is a protein induced by TNF-a and interleukin 6 (IL-6). Besides, PDIP1 can interact directly with proliferating cell nuclear antigen (PCNA) and the small subunit of DNA polymerase 5. The PDIP1 gene is also found in rat genome and has already been cloned. By searching the GeneBank EST database using the rat PDIP1 cDNA, we found a group of EST sequences that shared significant homologies with rat PDIP1, and we cloned the full length cDNA of the homologue gene of rat PDIP1 by RACE PCR, named it as rat PDIP1. The deduced protein of rat PDIP1 and PDIP1 share 65.1% sequence identity with each other and are highly conserved in majority of the middle portion of the two proteins, which encode a BTB/POZ domain at the N-terminus and a PCNA binding motif (QTKV-EFP) at the C-terminus, respectively. Since PDIP1 can interact with PCNA, in order to confirm the functional similarity between rat PDIP1 and PDIP1, we demonstrate the interaction between rat PDIP1 and PCNA by using GST pull-down, co-immunoprecipitation and subcellular colocalization assays. Because PDIP1 can be induced byTNF-a and TNF-a plays roles in liver regeneration, we used rat partial hepatectomy (PHx) models to study the expression of PDIP1 after the surgical removal of the liver at different recovery time-points and provide a basis for further functional studies of PDIP1 family.