Proliferating Cell Nuclear Antigen (PCNA) May Function as a Double Homotrimer Complex in the Mammalian Cell

Abstract

The diverse function of proliferating cell nuclear antigen (PCNA) may be regulated by interactions with different protein partners. Interestingly, the binding sites for all known PCNA-associating proteins are on the outer surface or the C termini ("front") sides of the PCNA trimer. Using cell extracts and purified human PCNA protein, we show here that two PCNA homotrimers form a back-to-back doublet. Mutation analysis suggests that the Arg-5 and Lys-110 residues on the PCNA back side are the contact points of the two homotrimers in the doublet. Furthermore, short synthetic peptides encompassing either Arg-5 or Lys-110 inhibit double trimer formation. We also found that a PCNA double trimer, but not a homotrimer alone, can simultaneously accommodate chromatin assembly factor-1 and polymerase ␦. Together, our data supports a model that chromatin remodeling by chromatin assembly factor-1 (and, possibly, many other cellular activities) are tightly coupled with DNA replication (and repair) through a PCNA double trimer complex.

Human hepatocellular carcinoma expresses specific PCNA isoforms: an in vivo and in vitro evaluation

“…44,45 Additionally, PCNA was previously detected as dimer and trimer on 2D SDS-PAGE 42 and, more recently, double trimeric structure was described. 31,32 Our findings therefore agree with those reported in the literature.…”

“…[24][25][26][27][28][29] Other than forming a homotrimeric structure, PCNA also has been found to form double homotrimeric complexes. [30][31][32] As each monomer has specific protein binding sites, the polymeric structure allows PCNA to bind different partners suggesting that the aggregation status may be relevant for its functions.…”

Proliferating cell nuclear antigen in the cytoplasm interacts with components of glycolysis and cancer

“…Proliferating cell nuclear antigen (PCNA) is central for many essential cellular processes such as DNA replication and damage repair, transcription, chromosome segregation, and cell-cycle progression [1][2][3][4][5][6][7][8]. All of these functions are carried out by PCNA in the nucleus.…”

“…Data obtained by several different techniques demonstrated that PCNA molecules form a single or double homotrimer complex that encircles the DNA fiber, and functions as a sliding clamp for DNA polymerases and a docking station for many protein partners [3,[10][11][12][13][14][15]. A PCNA ring may bind to different protein partners at different time and space to carry out specific tasks [3,5,16,17].…”

“…A PCNA ring may bind to different protein partners at different time and space to carry out specific tasks [3,5,16,17]. We previously found that the level of PCNA is substantially elevated in cancer cells, which is only notable difference between cancer and normal cells with respect to PCNA protein [18].…”