Alternative titles; symbols
HGNC Approved Gene Symbol: CHTF8
Cytogenetic location: 16q22.1 Genomic coordinates (GRCh38) : 16:69,118,010-69,132,588 (from NCBI)
CHTF18 (613201), CHTF8, and DCC1 (DSCC1; 613203) are components of an alternative replication factor C (RFC) (see 600404) complex that loads PCNA (176740) onto DNA during S phase of the cell cycle (Merkle et al., 2003; Bermudez et al., 2003).
By searching a human database for sequences similar to S. cerevisiae Ctf8, Merkle et al. (2003) identified human CHTF8. The deduced protein contains 3 leucine zipper motifs. Immunohistochemical analysis showed that CHTF18, CHTF8, and DCC1 localized to nuclear heterochromatin in a diffuse manner and appeared less abundant in nucleoli.
Bermudez et al. (2003) determined that the CHTF8 protein contains 121 amino acids and has a calculated molecular mass of 14 kD.
By coimmunoprecipitation analysis, Merkle et al. (2003) found that CHTF18, CHTF8, and DCC1 associated with each other and with the RFC3 (600405) subunit, suggesting that these proteins may function as a clamp loader complex. CHTF18, CHTF8, and DCC1 also selectively bound PCNA.
By immunoprecipitating proteins that associated with epitope-tagged CTF18 from human 293T cells, Bermudez et al. (2003) determined that CTF18 was a component of a 7-subunit cohesion-RFC complex, which they called CTF18-RFC. This complex also included stoichiometric amounts of DCC1, CTF8, and RFC2 (600404), RFC3, RFC4 (102577), and RFC5 (600407) subunits. These 7 subunits also assembled into a 5-subunit complex of CTF18, RFC2-5, and a DCC1-CTF8 dimer. Assembly of in vitro-translated components showed that CTF8 bound CTF18 in the 5-subunit complex, but not CTF18 alone, and the addition of DCC1 stabilized the completed 7-subunit CTF18-RFC complex. Both the 5- and 7-subunit CTF18-RFC complexes showed weak DNA-dependent ATPase activity that was stimulated by primed single-stranded DNA. Maximal stimulation of ssDNA-dependent ATPase activity required addition of RPA (see 179837) and PCNA. Both the 7- and 5-subunit CTF18-RFC complexes loaded PCNA onto primed and gapped circular DNA, but not onto single-stranded circular DNA or onto singly nicked circular DNA. CTF18-RFC also released PCNA that was preloaded onto DNA in an ATP-dependent manner. Both CTF18-RFC complexes supported PCNA-dependent DNA polymerase delta (see 174761)-catalyzed elongation of singly primed DNA. Bermudez et al. (2003) concluded that the CTF18-RFC complex functions as a PCNA clamp loader and may link sister chromatid cohesion with DNA replication.
Through single-molecule analysis, Terret et al. (2009) demonstrated that the RFC-CTF18 clamp loader controls the velocity spacing and restart activity of replication forks in human cells and is required for robust acetylation of cohesin's SMC3 subunit (606062) and sister chromatid cohesion. Unexpectedly, Terret et al. (2009) discovered that cohesin acetylation itself is a central determinant of fork processivity, as slow-moving replication forks were found in cells lacking the Eco1-related acetyltransferases ESCO1 (609674) or ESCO2 (609353) (including those derived from Roberts syndrome (268300) patients, in whom ESCO2 is biallelically mutated), and in cells expressing a form of SMC3 that cannot be acetylated. This defect was a consequence of cohesin's hyperstable interaction with 2 regulatory cofactors, WAPL (610754) and PDS5A (613200); removal of either cofactor allowed forks to progress rapidly without ESCO1, ESCO2, or RFC-CTF18. Terret et al. (2009) concluded that their results showed a novel mechanism for clamp loader-dependent fork progression, mediated by the posttranslational modification and structural remodeling of the cohesin ring. Loss of this regulatory mechanism leads to the spontaneous accrual of DNA damage and may contribute to the abnormalities of the Roberts syndrome cohesinopathy.
Hartz (2009) mapped the CHTF8 gene to chromosome 16q22.1 based on an alignment of the CHTF8 sequence (GenBank BM820172) with the genomic sequence (GRCh37).
Bermudez, V. P., Maniwa, Y., Tappin, I., Ozato, K., Yokomori, K., Hurwitz, J. The alternative Ctf18-Dcc1-Ctf8-replication factor C complex required for sister chromatid cohesion loads proliferating cell nuclear antigen onto DNA. Proc. Nat. Acad. Sci. 100: 10237-10242, 2003. [PubMed: 12930902] [Full Text: https://doi.org/10.1073/pnas.1434308100]
Hartz, P. A. Personal Communication. Baltimore, Md. 12/30/2009.
Merkle, C. J., Karnitz, L. M., Henry-Sanchez, J. T., Chen, J. Cloning and characterization of hCTF18, hCTF8, and hDCC1: Human homologs of an Saccharomyces cerevisiae complex involved in sister chromatid cohesion establishment. J. Biol. Chem. 278: 30051-30056, 2003. [PubMed: 12766176] [Full Text: https://doi.org/10.1074/jbc.M211591200]
Terret, M.-E., Sherwood, R., Rahman, S., Qin, J., Jallepalli, P. V. Cohesin acetylation speeds the replication fork. Nature 462: 231-234, 2009. [PubMed: 19907496] [Full Text: https://doi.org/10.1038/nature08550]