Differential expression of human placental growth-hormone variant and chorionic somatomammotropin in culture.
Regulation of human placental growth-hormone variant (hGH-V) in the presence of its own promoter has been studied. At term, 10-20% of placental mRNA is specific for chorionic somatomammotropin (hCS-A and -B) compared with 0.05% hGH-V, yet these genes show more than 90% sequence similarity at the nucleotide level. By using stable gene transfer of intact hGH-V and hCS-A genes into rat pituitary (GC) cells, synthesis and release of hGH-V and hCS are detected. This suggests that hGH-V as well as hCS is secreted during pregnancy. The hCS-A mRNA level is higher than that observed from the hGH-V gene in stably transfected GC cells. Also, a hybrid gene containing hGH-V 5'-flanking DNA was less active than a hybrid hCS-A gene containing equivalent sequences after transient transfection of these cells. This correlates with the binding of a known transcription factor to a proximal region (-97/-66) of the hCS-A promoter, and not the equivalent hGH-V gene sequences. These results indicate that differential expression of hGH-V and hCS in GC cells is related, in part, to the strength of their respective promoters, and suggest a similar mechanism may exist in the placenta.
Nickel
B E
BE
Department of Physiology, University of Manitoba, Winnipeg, Canada.
Kardami
E
E
Cattini
P A
PA
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D010920:Placenta / Q000201:enzymology*; D010928:Placental Lactogen / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection
D012333:RNA, Messenger; D014157:Transcription Factors; D013006:Growth Hormone; D010928:Placental Lactogen