HGNC Approved Gene Symbol: TREX2
Cytogenetic location: Xq28 Genomic coordinates (GRCh38) : X:153,444,473-153,446,056 (from NCBI)
The multistep processes of DNA replication, repair, and recombination require the excision of nucleotides from DNA 3-prime termini. Enzymes containing 3-prime-to-5-prime exonuclease activity, such as TREX2, remove mismatched, modified, fragmented, and normal nucleotides to generate the appropriate 3-prime termini for subsequent steps in the DNA metabolic pathways.
By micropeptide sequence analysis of the 30-kD bovine Trex1 protein, PCR with degenerate primers, and EST database searching, Mazur and Perrino (1999) obtained cDNAs encoding mouse and human TREX1 (606609) and TREX2. Sequence analysis predicted that the 236-amino acid TREX2 protein is 44% identical to TREX1. TREX2 contains 3 conserved exonuclease motifs, with an HxAxxD sequence in the third motif.
Mazur and Perrino (2001) used 5-prime RACE to identify the flanking region of TREX2. RT-PCR analysis detected ubiquitous expression of TREX2.
Functional analysis by Mazur and Perrino (1999) confirmed that the 3-prime-to-5-prime exonuclease activity of the recombinant TREX2 protein is comparable to that of the native protein and prefers mismatched 3-prime termini. Mazur and Perrino (1999) concluded that the TREX proteins are small, independent 3-prime excision enzymes, whereas the multifunctional p53 (191170) and WRN (RECQL2; 604611) proteins, which also have 3-prime-to-5-prime exonuclease activity, are much larger.
Hu et al. (2013) delineated 2 pathways that spontaneously fuse inverted repeats to generate unstable chromosomal rearrangements in wildtype mouse embryonic stem cells. Gamma radiation induced a RECQL3 (604610)-regulated pathway that selectively fused identical, but not mismatched, repeats. By contrast, ultraviolet light induced a RAD18 (605256)-dependent pathway that efficiently fused mismatched repeats. In addition, TREX2, a 3-prime-to-5-prime exonuclease, suppressed identical repeat fusion but enhanced mismatched repeat fusion, clearly separating these pathways. TREX2 associated with UBC13 (603679) and enhanced PCNA (176740) ubiquitination in response to ultraviolet light, consistent with its being a novel member of error-free postreplication repair. RAD18 and TREX2 also suppressed replication fork stalling in response to nucleotide depletion. Replication fork stalling induced fusion for identical and mismatched repeats, implicating faulty replication as a causal mechanism for both pathways.
By genomic sequence analysis, Mazur and Perrino (2001) mapped the TREX2 gene to chromosome Xq28.
Hu, L., Kim, T. M., Son, M. Y., Kim, S.-A., Holland, C. L., Tateishi, S., Kim, D. H., Yew, P. R., Montagna, C., Dumitrache, L. C., Hasty, P. Two replication fork maintenance pathways fuse inverted repeats to rearrange chromosomes. Nature 501: 569-572, 2013. [PubMed: 24013173] [Full Text: https://doi.org/10.1038/nature12500]
Mazur, D. J., Perrino, F. W. Structure and expression of the TREX1 and TREX2 3-prime-to-5-prime exonuclease genes. J. Biol. Chem. 276: 14718-14727, 2001. [PubMed: 11278605] [Full Text: https://doi.org/10.1074/jbc.M010051200]
Mazur, D. J., Perrino, F. W. Identification and expression of the TREX1 and TREX2 cDNA sequences encoding mammalian 3-prime-to-5-prime exonucleases. J. Biol. Chem. 274: 19655-19660, 1999. [PubMed: 10391904] [Full Text: https://doi.org/10.1074/jbc.274.28.19655]