G2E3 is a nucleo-cytoplasmic shuttling protein with DNA damage responsive localization

Abstract

G2E3 was originally described as a G2/M-specific gene with DNA damage responsive expression. The presence of a conserved HECT domain within the carboxy-terminus of the protein indicated that it likely functions as an ubiquitin ligase or E3. Although HECT domains are known to function in this capacity for many proteins, we demonstrate that a portion of the HECT domain from G2E3 plays an important role in the dynamic subcellular localization of the protein. We have shown that G2E3 is a nucleo-cytoplasmic shuttling protein with nuclear export mediated by a novel nuclear export domain that functions independently of CRM1. In full-length G2E3, a separate region of the HECT domain suppresses the function of the NES. Additionally, G2E3 contains a nucleolar localization signal (NoLS) in its amino terminus. Localization of G2E3 to the nucleolus is a dynamic process, and the protein delocalizes from the nucleolus rapidly after DNA damage. Cell cycle phase-specific expression and highly regulated subcellular localization of G2E3 suggest a possible role in cell cycle regulation and the cellular response to DNA damage.

G2E3 Is a Dual Function Ubiquitin Ligase Required for Early Embryonic Development

“…G2E3 displays dynamic subcellular localization, concentrating within nucleoli but relocalizing to the nucleoplasm after genotoxic stress (19). These data suggest a possible role for G2E3 in regulation of mitosis and the response to DNA damage.…”

“…Because protein ubiquitination plays an essential role in many aspects of cell cycle regulation and checkpoint function, it is not surprising that many of the genes identified in our study are thought to function in this process. Included among these are an APC/C component (Cdc20) (15,16), an SCF component (Tome-1) (10), the ubiquitin conjugating enzymes E2-EPF (17,18), and UBE2Q2 (12), and a putative ubiquitin ligase known as G2E3 (19).…”

PBK/TOPK interacts with the DBD domain of tumor suppressor p53 and modulates expression of transcriptional targets including p21

“…Among these were p21 (Bunz et al, 1998;Wendt et al, 2006), DUSP1 (Li et al, 2003) PBK/TOPK and p53 functional interactions F Hu et al (Pohl et al, 1999), FAS (Mu¨ller et al, 1998;Pohl et al, 1999), CASP10 (Rikhof et al, 2003) (all upregulated), and Bcl-xL (Bartke et al, 2001), which was downregulated. G2E3 (Brooks et al, 2007(Brooks et al, , 2008, a newly characterized gene involved in G 2 /M cell-cycle progression, was found to be suppressed by PBK knockdown, but its association to p53 is unknown. We validated the microarray analysis results for all nine genes by qRT-PCR (see Table 1 and Supplementary Figure S4).…”

Identifying long-range control elements of the BRCA1 promoter

“…Furthermore, interphase FISH could be performed in various conditions such as +/-E2 treatment. Since BRCA1 and G2E3 are both involved in DNA repair, the PRE2 interaction with the BRCA1 promoter might also change upon DNA damage [247]. To examine if 3C interaction profiles change upon DNA damage, 3C libraries can be generated from MCF7 cells +/-doxorubicin, a DNA intercalating agent that induces double stranded DNA breaks or ionising radiation treatment [313].…”

“…These candidate genes were; NCDN (Neurochondrin) [244], MDK (Midkine) [245],PXN (Paxillin) [246] and G2E3 (G2/M-phase specific E3 ubiquitin protein ligase) [247,248].…”