Alternative titles; symbols
HGNC Approved Gene Symbol: HMG20B
Cytogenetic location: 19p13.3 Genomic coordinates (GRCh38) : 19:3,572,944-3,579,083 (from NCBI)
High mobility group (HMG) proteins, such as HMG20B, are nonhistone chromosomal proteins that contain a conserved DNA-binding domain called the HMG box (summary by Sumoy et al., 2000). See HMG2 (163906) for additional information on HMG proteins.
By EST database searching for sequences homologous to HMG20A (605534), Sumoy et al. (2000) identified a novel member of the HMG family, which they designated HMG20B. The longest cDNA obtained encodes a deduced 317-amino acid protein. Northern blot analysis detected 2 major transcripts of approximately 2.6 and 1.5 kb. The highest expression of the 1.5-kb form was found in prostate, testis, heart, and kidney, while brain, spleen, lung, skeletal muscle, and leukocytes showed lower levels. Within the brain, it was expressed almost uniformly, with increased levels in the corpus callosum and hippocampus. The 2.6-kb transcript was expressed at lower levels and was found in thymus, prostate, placenta, liver, kidney, and pancreas.
Germline mutations of the BRCA2 gene (600185) confer susceptibility to breast cancer. Marmorstein et al. (2001) isolated a 2-MD BRCA2-containing complex from HeLa cells and, using mass spectrometry, identified a structural DNA-binding component they designated BRAF35. The 317-amino acid BRAF35 protein contains a nonspecific DNA-binding HMG domain and a kinesin-like coiled-coil domain. The only protein with structural domains similar to those of BRAF35 was BAF57 (603111), a subunit of the SWI/SNF complex. In situ hybridization showed that similar to BRCA2, BRAF35 mRNA expression levels in mouse embryos were highest in proliferating tissues with high mitotic index. Strikingly, nuclear staining revealed a close association of the BRAF35-BRCA2 complex with condensed chromatin coincident with histone H3 (see 602810) phosphorylation. Antibody microinjection experiments suggested a role for the BRCA2-BRAF35 complex in modulation of cell cycle progression.
Sumoy et al. (2000) inferred the map position of HMG20B from genomic clone sequence annotation to be in 19p13.3, between D19S209 and D19S216 (Deloukas et al., 1998).
Deloukas, P., Schuler, G. D., Gyapay, G., Beasley, E. M., Soderlund, C., Rodriguez-Tome, P., Hui, L., Matise, T. C., McKusick, K. B., Beckmann, J. S., Bentolila, S., Bihoreau, M.-T., and 53 others. A physical map of 30,000 human genes. Science 282: 744-746, 1998. [PubMed: 9784132] [Full Text: https://doi.org/10.1126/science.282.5389.744]
Marmorstein, L. Y., Kinev, A. V., Chan, G. K. T., Bochar, D. A., Beniya, H., Epstein, J. A., Yen, T. J., Shiekhattar, R. A human BRCA2 complex containing a structural DNA binding component influences cell cycle progression. Cell 104: 247-257, 2001. [PubMed: 11207365] [Full Text: https://doi.org/10.1016/s0092-8674(01)00209-4]
Sumoy, L., Carim, L., Escarceller, M., Nadal, M., Gratacos, M., Pujana, M. A., Estivill, X., Peral, B. HMG20A and HMG20B map to human chromosomes 15q24 and 19p13.3 and constitute a distinct class of HMG-box genes with ubiquitous expression. Cytogenet. Cell Genet. 88: 62-67, 2000. [PubMed: 10773667] [Full Text: https://doi.org/10.1159/000015486]