Alternative titles; symbols
HGNC Approved Gene Symbol: ACTR8
Cytogenetic location: 3p21.1 Genomic coordinates (GRCh38): 3:53,858,992-53,882,152 (from NCBI)
ACTR8 is an actin-related DNA-binding protein that is a component of the INO80 chromatin remodeling complex (see INO80, 610169) (Osakabe et al., 2014).
Aoyama et al. (2008) stated that human ACTR8, which they called ARP8, is a 625-amino acid actin family protein. Compared with the actin fold, the basal structure of actin family proteins, ACTR8 has 5 inserted sequences (I through V). Immunofluorescence analysis revealed that human ARP8 localized to interphase nuclei and mitotic chromosomes in HeLa cells. Mutation analysis showed that a region containing insertions II and III was necessary for localization of ARP8 to mitotic chromosomes, and that insertion I was required for nuclear localization during interphase.
Gross (2022) mapped the ACTR8 gene to chromosome 3p21.1 based on an alignment of the ACTR8 sequence (GenBank BC032744) with the genomic sequence (GRCh38).
Using localization and immunoprecipitation analyses, Aoyama et al. (2008) showed that ARP8 was a component of the INO80 complex with INO80 and ARP5 (ACTR5; 619730) and that it functioned in mitosis. In mitotic cells, the INO80 complex was at least partially disassembled, as ARP8 and ARP5 interacted in the complex during interphase, but ARP5 dissociated from ARP8 in mitotic cells. Knockdown of ARP8, but not INO80 or ARP5, caused abnormal chromosome alignment in HeLa cells, indicating that ARP8 function at mitotic chromosomes was independent of INO80 complex activity.
By immunoblot and immunostaining analyses, Kashiwaba et al. (2010) showed that the INO80 complex was recruited to DNA damage sites in mouse and human cells, like in yeast. Knockdown analysis revealed that recruitment of the complex to DNA damage sites required ARP8.
By knockout of ARP5 or ARP8 in the human Nalm-6 pre-B cell line, Takahashi et al. (2017) showed that the INO80 complex was involved in oxidative stress-induced expression of HMOX1 (141250), as well as many other genes. The INO80 complex bound to regulatory sites of the HMOX1 gene in response to oxidative stress. ARP8 contributed to binding of the INO80 complex to chromatin, whereas ARP5 was required for remodeling of chromatin at HMOX1 regulatory sites and transcriptional activator binding at these sites.
Using purified recombinant protein, Osakabe et al. (2014) demonstrated that human ARP8 bound to DNA, with a preference for single-stranded DNA, and formed stable complexes. The N-terminal extension of ARP8 was required for stable binding to DNA, but multiple regions protruding from the actin fold also contributed to DNA binding. The ATP-binding pocket of ARP8 appeared to be play a regulatory role in binding of ARP8 to DNA in the presence of ATP. Knockout and overexpression analysis in human Nalm-6 cells showed that ARP8 was required for normal cell growth, and that loss of ARP8 impaired DNA repair activity.
Gerhold et al. (2012) determined the crystal structure of human ARP8 lacking the first 31 residues at 2.6-angstrom resolution. The crystals contained 1 ARP8 molecule per asymmetric unit, a bound ATP molecule, and 1 coordinated metal ion. The ARP8 structure displayed a typical actin fold with a central nucleotide-binding cleft and showed the flattened disk-like shape of actin with concave and convex sides. However, unlike actin, ARP8 had several insertions in the conserved actin fold that made it impossible to polymerize. One such insertion also wrapped over the active-site cleft and appeared to rigidify the domain architecture of ARP8. ARP8 bound ATP strongly, but it showed low basal ATP hydrolysis activity, like actin, as the ARP8 active site shared features with actin and likely controlled ATPase activity allosterically. The solution structure of human ARP8 was monomeric, although ARP8 featured an N-terminal extension and had the potential for dimerization. Quantitative binding studies with nucleosomes and histone complexes revealed that ARP8 functioned as a nucleosome recognition module, and its interaction with nucleosomes and histone complexes was quantitatively different compared with ARP4 and INO80 subcomplex I.
Aoyama, N., Oka, A., Kitayama, K., Kurumizaka, H., Harata, M. The actin-related protein hArp8 accumulates on the mitotic chromosomes and functions in chromosome alignment. Exp. Cell Res. 314: 859-868, 2008. [PubMed: 18163988] [Full Text: https://doi.org/10.1016/j.yexcr.2007.11.020]
Gerhold, C. B., Winkler, D. D., Lakomek, K., Seifert, F. U., Fenn, S., Kessler, B., Witte, G., Luger, K., Hopfner, K.-P. Structure of actin-related protein 8 and its contribution to nucleosome binding. Nucleic Acids Res. 40: 11036-11046, 2012. [PubMed: 22977180] [Full Text: https://doi.org/10.1093/nar/gks842]
Gross, M. B. Personal Communication. Baltimore, Md. 1/21/2022.
Kashiwaba, S., Kitahashi, K., Watanabe, T., Onoda, F., Ohtsu, M., Murakami, Y. The mammalian INO80 complex is recruited to DNA damage sites in an ARP8 dependent manner. Biochem. Biophys. Res. Commun. 402: 619-625, 2010. [PubMed: 20971067] [Full Text: https://doi.org/10.1016/j.bbrc.2010.10.066]
Osakabe, A., Takahashi, Y., Murakami, H., Otawa, K., Tachiwana, H., Oma, Y., Nishijima, H., Shibahara, K., Kurumizaka, H., Harata, M. DNA binding properties of the actin-related protein Arp8 and its role in DNA repair. PLoS One 9: e108354, 2014. [PubMed: 25299602] [Full Text: https://doi.org/10.1371/journal.pone.0108354]
Takahashi, Y., Murakami, H., Akiyama, Y., Katoh, Y., Oma, Y., Nishijima, H., Shibahara, K., Igarashi, K., Harata, M. Actin family proteins in the human INO80 chromatin remodeling complex exhibit functional roles in the induction of heme oxygenase-1 with hemin. Front. Genet. 8: 17, 2017. [PubMed: 28270832] [Full Text: https://doi.org/10.3389/fgene.2017.00017]