Alternative titles; symbols
HGNC Approved Gene Symbol: MED22
Cytogenetic location: 9q34.2 Genomic coordinates (GRCh38): 9:133,338,312-133,348,131 (from NCBI)
MED22, or SURF5, is a component of the Mediator complex, which is a coactivator for DNA-binding factors that activate transcription via RNA polymerase II (Sato et al., 2003). For background information on the surfeit genes, see SURF1 (185620).
Garson et al. (1996) stated that the mouse Surf5 protein contains 140 amino acids and is 98.5% identical to the human SURF5 protein. By screening mouse brain and human fetal brain cDNA libraries, they cloned a splice variant of SURF5 that they called SURF5B. Both mouse and human SURF5B encode a deduced 200-amino acid protein that is identical to SURF5 over the first 137 amino acids. Northern blot analysis detected Surf5 expression in all mouse tissues examined, whereas expression of Surf5b was restricted to brain, heart, testis, and skeletal muscle. Both mouse proteins were recovered in the cytoplasmic fraction of transfected cells.
By PCR of a human teratocarcinoma cell line cDNA library, Angiolillo et al. (2002) obtained 3 splice variants of SURF5. The longest cDNA, SURF5a, encodes a deduced 140-amino acid protein with a calculated molecular mass of 16.7 kD. SURF5b encodes a deduced 200-amino acid protein with a calculated molecular mass of 21 kD. The first 137 amino acids of both proteins are identical. Northern blot analysis of human tissues detected a 2.7-kb SURF5a transcript in all tissues and cell lines examined. A 1.4-kb SURF5b transcript was detected only in heart, brain, skeletal muscle, and pancreas, and in human teratocarcinoma cells. Fluorescence-tagged SURF5a and SURF5b localized predominantly to the cytoplasm of transfected HeLa cells.
Using HeLa cells overexpressing epitope-tagged MED10 (612382), Sato et al. (2003) purified several components of the human Mediator complex, including MED22, which they called SURF5, and subsequently cloned the corresponding cDNA.
Garson et al. (1996) found that both mouse Surf5 and Surf5b were expressed in undifferentiated mouse teratocarcinoma cells, but that expression of Surf5b was upregulated 4-fold following their differentiation into neuronal cells.
Using in vitro-translated epitope-tagged proteins for protein-binding assays, Sato et al. (2003) found SURF5 directly interacted with the Mediator complex subunits TRAP25 (MED30; 610237), HSPC296 (MED11; 612383), TRAP80 (MED17; 603810), and TRAP37 (MED27; 605044). Formation of the SURF5-HSPC296 and SURF5-TRAP25 heterodimers were confirmed by coimmunoprecipitation analysis of cotransfected insect cells and E. coli, respectively.
Angiolillo et al. (2002) determined that the MED22 gene contains 5 exons and spans about 7.5 kb. The transcription start sites of the MED22 and SURF3 (RPL7A; 185640) genes are separated by a 110-bp region that showed bidirectional promoter activity. This promoter region lacks a TATA box but is characterized by a CpG island that extends through the first exon into the first intron of both genes.
By FISH analysis, Yon et al. (1993) identified the MED22 gene within the surfeit gene cluster in chromosome 9q34.
Angiolillo, A., Russo, G., Procellini, A., Smaldone, S., D'Alessandro, F., Pietropaolo, C. The human homologue of the mouse Surf5 gene encodes multiple alternatively spliced transcripts. Gene 284: 169-178, 2002. [PubMed: 11891058] [Full Text: https://doi.org/10.1016/s0378-1119(02)00379-7]
Garson, K., Duhig, T., Fried, M. Tissue-specific processing of the Surf-5 and Surf-4 mRNAs. Gene Expr. 6: 209-218, 1996. [PubMed: 9196076]
Sato, S., Tomomori-Sato, C., Banks, C. A. S., Sorokina, I., Parmely, T. J., Kong, S. E., Jin, J., Cai, Y., Lane, W. S., Brower, C. S., Conaway, R. C., Conaway, J. W. Identification of mammalian mediator subunits with similarities to yeast mediator subunits Srb5, Srb6, Med11, and Rox3. J. Biol. Chem. 278: 15123-15127, 2003. [PubMed: 12584197] [Full Text: https://doi.org/10.1074/jbc.C300054200]
Yon, J., Jones, T., Garson, K., Sheer, D., Fried, M. The organization and conservation of the human Surfeit gene cluster and its localization telomeric to the c-abl and can proto-oncogenes at chromosome band 9q34.1. Hum. Molec. Genet. 2: 237-240, 1993. [PubMed: 8499913] [Full Text: https://doi.org/10.1093/hmg/2.3.237]