HGNC Approved Gene Symbol: CGB2
Cytogenetic location: 19q13.33 Genomic coordinates (GRCh38): 19:49,031,890-49,033,238 (from NCBI)
The placental hormone chorionic gonadotropin (CG) is a member of a glycoprotein hormone family that includes the pituitary hormones luteinizing hormone (LH; 152780), follicle-stimulating hormone (FSH; 136530), and thyroid-stimulating hormone (TSH; 188540). Each of these hormones consists of a noncovalent dimer of alpha and beta subunits. The alpha subunit is the same for all 4 hormones (see CGA; 118850), and the beta subunits define the endocrine function of the dimer (Talmadge et al., 1983).
By restriction digest analysis, Talmadge et al. (1983) determined that the 7 CGB genes are extremely similar but not identical. Bo and Boime (1992) determined that most of the sequence variation among the CGB genes occurs in the nontranslated region of exon 1. They noted that CGB2 and CGB1 (608823) were thought to be pseudogenes; however, RT-PCR of first trimester placenta and placenta polysomal RNA detected both CGB1 and CGB2. Expression in polysomal RNA suggested that the transcripts are translated. Northern blot analysis detected lower expression of these transcripts in comparison to those of other CGBs, and transcripts were smaller owing to the use of a cryptic splice site. The open reading frames were also significantly different than those of other CGBs.
Jameson and Lindell (1988) determined that each of the CGB genes contains 3 exons. Otani et al. (1988) determined that the promoter regions contain no CAAT or TATAA boxes. Policastro et al. (1983) observed that CGB2 contains a noncanonic donor splice sequence at the exon 1-intron 1 boundary.
Talmadge et al. (1983) mapped the CGB2 gene to a gene cluster that contains 7 CGB genes and LHB (152780). This gene cluster is located on chromosome 19q13.32. Jameson and Lindell (1988) determined that the CGB gene cluster spans 68 kb.
Bo, M., Boime, I. Identification of the transcriptionally active genes of the chorionic gonadotropin beta gene cluster in vivo. J. Biol. Chem. 267: 3179-3184, 1992. [PubMed: 1371113]
Jameson, J. L., Lindell, C. M. Isolation and characterization of the human chorionic gonadotropin beta subunit (CG-beta) gene cluster: regulation of a transcriptionally active CG-beta gene by cyclic AMP. Molec. Cell. Biol. 8: 5100-5107, 1988. [PubMed: 2468994] [Full Text: https://doi.org/10.1128/mcb.8.12.5100-5107.1988]
Otani, T., Otani, F., Krych, M., Chaplin, D. D., Boime, I. Identification of a promoter region in the CG-beta gene cluster. J. Biol. Chem. 263: 7322-7329, 1988. Note: Erratum: J. Biol. Chem. 263: 19256-19257, 1988. Note: Erratum: J. Biol. Chem. 263: 19256-19257, 1988. [PubMed: 2452822]
Policastro, P., Ovitt, C. E., Hoshina, M., Fukuoka, H., Boothby, M. R., Boime, I. The beta subunit of human chorionic gonadotropin is encoded by multiple genes. J. Biol. Chem. 258: 11492-11499, 1983. [PubMed: 6194155]
Talmadge, K., Boorstein, W. R., Fiddes, J. C. The human genome contains seven genes for the beta-subunit of chorionic gonadotropin but only one gene for the beta-subunit of luteinizing hormone. DNA 2: 281-289, 1983. [PubMed: 6319099] [Full Text: https://doi.org/10.1089/dna.1983.2.281]