Dynamic changes in nuclear localization of a DNA-binding protein tyrosine phosphatase TCPTP in response to DNA damage and replication arrest

Abstract

TCPTP is an ubiquitously expressed tyrosine phosphatase with a predominant nuclear isoform (TC45) that binds DNA and has a role in G1-S cell cycle progression. Its deregulation by overexpression induces p53-dependent apoptosis, but the physiological role of its DNA-binding function is not known. Using immunocytochemistry and subcellular fractionation, we investigated changes in its localization in response to DNA damage and replication arrest. Rat fibroblasts showed an increase in endogenous TCPTP bound to nuclear components 3 h after exposure to sublethal dose of UV irradiation. Fractionation of nuclei showed an increase in chromatin and nuclear matrix associated component of TC45. After UV treatment, cells showed a concentration of TCPTP in discrete foci and enhanced colocalization with PCNA and p53BP1. Cells arrested at G1-S transition by hydroxyurea showed a loss of the predominant nuclear staining of TCPTP and an increase in cytoplasmic staining. Upon release from replication block, there was a time-dependent increase in number of cells showing prominent nuclear localization. This change in localization coincides with that of PCNA and Cdk2, two other nuclear proteins having functions in DNA replication. These results provide evidence for the regulation of TCPTP in response to DNA damage and replication stress. Dynamic changes in its localization coincident with that of PCNA suggest involvement of TCPTP in DNA repair and replication.

Loss of DUSP3 activity radiosensitizes human tumor cell lines via attenuation of DNA repair pathways

“…More importantly, in addition to DUSP3, several tyrosine protein phosphatases have been directly or indirectly linked to the DNA damage response and repair mechanisms. For instance, the TC45 isoform of TCPTP binds to DNA and is involved in G1-S cell cycle progression [66]. Further, three enzymes, CDC25A/B/C, which are class III PTPs, were the first nuclear dual-specificity phosphatases shown to regulate cell cycle progression via the dephosphorylation of CDKs [67].…”

UVB-induced nuclear translocation of TC-PTP by AKT/14-3-3σ axis inhibits keratinocyte survival and proliferation

“…Studies performed using TC-PTP knockout mice showed its critical role in hematopoiesis and immune function because TC-PTP knockout mice were severely defective in the hematopoietic compartment and all homozygous mice died between 3 and 5 weeks of age due to diarrhea, splenomegaly, lymphadenopathy, and anemia [ 5 ]. TC-PTP is also involved in the regulation of the cell cycle [ 6 - 8 ]. Furthermore, TC-PTP has a role in the regulation of diabetes and obesity by modulating insulin and leptin signaling [ 9 - 12 ].…”

The Nuclear Matrix: Fractionation Techniques and Analysis

“…CSK was first used by Lenk et al (1977) and later by Capco et al (1982) for electron microscopy. Others have used it for immunodetection of individual nuclear matrix components (Nickerson et al 1992;Grondin et al 1996;Huang et al 2004;Boisvert et al 2005;Ainscough et al 2007;Campalans et al 2007), identification of protein domains required for nuclear matrix binding (Ainscough et al 2007), analysis of temporally regulated recruitment (Fujita 1999;Fujita et al 2002;Miccoli et al 2003;Samaniego et al 2006;Sree et al 2012), and comparison of recruitment between developmental or differentiation stages and between disease states (Munkley et al 2011). The benefits of this method include relatively gentle buffer conditions, the potential to generate robust results by using imaging and biochemical analysis in parallel, and its flexibility to incorporate high salt to reveal the core nuclear matrix or pretreatment with a protein-protein crosslinker to reveal those proteins only weakly associated with the nuclear matrix.…”