Peptide hormone regulation of prolactin gene expression.
Item
-
Title
-
Peptide hormone regulation of prolactin gene expression.
-
Identifier
-
AAI9315517
-
identifier
-
9315517
-
Creator
-
Yan, Guo-Zai.
-
Contributor
-
Adviser: Carter Bancroft
-
Date
-
1993
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Engineering, Biomedical | Chemistry, Biochemistry | Biology, Molecular
-
Abstract
-
Transfection experiments with rat pituitary GH{dollar}\sb3{dollar} cells were employed to show that two TRH response elements (TRHREs) in the PRL proximal promoter correspond to binding sites for the pituitary cell-specific transcription factor pit-1. Either mutation of the strongest TRHRE, site 1P, or coexpression of a dominant mutant pit-1 possessing reduced trans-activational activity, strongly inhibited TRH regulation of PRL promoter constructs, implying that the cell-specific activator pit-1 is a gene-proximal mediator of TRH action on the PRL gene. Similar experiments showed that site 1P is also a Ca{dollar}\sp{lcub}2+{rcub}{dollar} response element, and that pit-1 also represents the gene-proximal protein that transduces the Ca{dollar}\sp{lcub}2+{rcub}{dollar} signal to the PRL promoter. Pharmacological experiments implied that Ca{dollar}\sp{lcub}2+{rcub}{dollar} but not protein kinase C (PKC) activity is required for TRH action on the PRL promoter. Thus, Ca{dollar}\sp{lcub}2+{rcub}{dollar} is apparently a mediator of TRH regulation of PRL gene expression, but not via a pathway involving PKC.;To examine the generality of these results, regulation of transfected PRL promoter constructs by another significant PRL gene activator, vasoactive intestinal peptide (VIP), was also examined. 5{dollar}\sp\prime{dollar}-deletion analysis showed that the first 174 base pairs of the PRL promoter is required for induction by VIP. Pharmacological studies of VIP regulation of the PRL promoter yielded the following results: The use of cellular Ca{dollar}\sp{lcub}2+{rcub}{dollar} blockers implied that Ca{dollar}\sp{lcub}2+{rcub}{dollar} is a mediator of VIP stimulation of the PRL promoter. Down-regulation of PKC did not inhibit induction of PRL promoter expression by VIP, implying that regulation of PRL gene expression by VIP is also independent of PKC activity. Inhibition of cAMP-dependent protein kinase A (PKA) also did not block VIP induction of PRL promoter expression, suggesting that PKA also does not play a major role in this action of VIP.;The present studies showed that CREB can act as a specific repressor of PRL promoter activity in GH{dollar}\sb3{dollar} cells, and can repress pit-1 activation of the PRL promoter in the non-pituitary C6 rat glial cells. In either pituitary or non-pituitary cells, this repression can be reversed by co-expression of PKA. These results suggest that CREB may act by competing for binding to the PRL CLE with a factor which is required for pit-1 activation of the PRL promoter.;The present studies showed that either PKA or a constitutively active form of CREB (CREB-VP16) are capable of transactivating the PRL promoter through the PRL CLE site in C6 rat glial cells. (Abstract shortened by UMI.).
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
