A single gene encodes the beta-subunits of equine luteinizing hormone and chorionic gonadotropin

Abstract

Equine (e) CG and LH beta-subunits have identical amino acid sequences, including an extended carboxyl-terminal peptide (CTP). This suggests that unlike the corresponding human genes, the beta-subunits of eCG and eLH may be encoded by a single gene and share a common proximal promotor region. To explore this, we isolated and characterized the eLH/CG beta gene(s). Data from Southern analyses suggest that the eCG beta and eLH beta subunits are products of the same single copy gene (eLH/CG beta). Overlapping fragments of the eLH/CG beta gene and cDNA were amplified from equine genomic DNA and pituitary gland mRNA by the polymerase chain reaction, cloned, and sequenced. The eLH/CG beta gene spans less than 1.2 kilobase-pairs and has three exons that translate a CTP-containing polypeptide identical in sequence to that previously reported for the mature equine protein. There is, however, little amino acid homology shown between the CTP of human or equine CG beta subunit. In addition, unlike the human genes, the same TATAA-like element appears to be involved in directing initiation of transcription of the eLH/CG beta gene in placenta and anterior pituitary. Based upon these differences, we suggest that the CG beta genes evolved independently in humans and equids and that different mechanisms are involved in their patterns of placenta-specific expression.

Biological Activities of Tethered Equine Chorionic Gonadotropin (eCG) and Its Deglycosylated Mutants

“…This hormone family is characterized by a heterodimeric structure composed of a common α-subunit noncovalently linked to a hormone-specific β-subunit [1]. The β-subunits of eCG and eLH, translated from the same gene, have identical primary structures [2,3]. The difference between eCG and eLH lies in the structure of their carbohydrates, which are both sialylated and sulfated in LH and sialylated in CG [4,5].…”

“…The β-subunits of eCG and eLH, translated from the same gene, have identical primary structures [2,3]. The difference between eCG and eLH lies in the structure of their carbohydrates, which are both sialylated and sulfated in LH and sialylated in CG [4,5].…”

Molecular characterization, modeling, in silico analysis of equine pituitary gonadotropin alpha subunit and docking interaction studies with ganirelix

“…However in contrast to primates and other farm animals, in horses, both LH and CG b subunits are encoded by the same gene (Sherman et al 1992). Both the pituitary eLH and placental eCG display the dual LH and FSH like activity in nonequine species with identical FSH/LH activity ratios (Chopineau et al 1993).…”

Involvement of equine chorionic gonadotropin (eCG) carbohydrate side chains in its bioactivity; lessons from recombinant hormone expressed in insect cells

“…Within the same species, the α-subunit is encoded by a single gene and is common to all glycoprotein hormones whereas different genes encode β-subunits, which confer specificity to the glycoprotein hormone heterodimers [2,3]. In horses, in contrast to primates, both LH and CG β-subunits are encoded by the same gene [4] and consequently the recombinant hormone is called eLH/CG. Both placental eCG and pituitary eLH exhibit dual LH and FSH in non equine species with identical FSH/LH activity ratios [5].…”