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Identification of a hormonally regulated luteinizing hormone/human chorionic gonadotropin receptor mRNA binding
1Departments of Biological Chemistry and Obstetrics/Gynecology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0617, USA.
Abstract:
To elucidate the molecular events associated with the regulation of luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor mRNA stability during hCG-induced receptor down-regulation, we have identified an LH/hCG receptor-specific mRNA binding protein. Proteins were isolated from control and down-regulated rat ovary and were incubated with in vitro transcribed RNAs corresponding to the full-length LH/hCG receptor, as well as 5'- and 3'-truncated receptor forms. Resultant ribonucleoprotein complexes were analyzed by RNA gel mobility shift. A prominent Mr 50,000 ribonucleoprotein complex was identified with the following characteristics: 1) specificity for LH/hCG receptor open reading frame sequences located between nucleotides 102 and 282; 2) lack of competition by nonspecific RNAs; 3) a 3-fold increase in RNA binding activity during hCG-induced receptor down-regulation; and 4) limited tissue expression. This report describes the first evidence of an LH/hCG receptor mRNA binding protein, which we term LRBP-1, for luteinizing hormone receptor RNA binding protein-1. This protein is a candidate for a trans-acting factor involved in the hormonal regulation of LH/hCG receptor mRNA stability in rat ovary.
Insights
Researchers identified a novel protein, luteinizing hormone receptor RNA binding protein-1 (LRBP-1), that binds to LH/hCG receptor mRNA. This binding increases during hCG-induced receptor down-regulation, suggesting LRBP-1
Area of Science:
- Endocrinology
- Molecular Biology
- Reproductive Biology
Background:
- Luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor down-regulation is a critical process in reproductive physiology.
- The molecular mechanisms controlling LH/hCG receptor mRNA stability during this down-regulation are not fully understood.
Purpose of the Study:
- To identify and characterize proteins that bind to LH/hCG receptor mRNA.
- To investigate the role of these proteins in regulating LH/hCG receptor mRNA stability.
Main Methods:
- Proteins were isolated from rat ovaries under control and hCG-down-regulated conditions.
- RNA gel mobility shift assays were used to detect ribonucleoprotein complexes.
- In vitro transcribed RNAs corresponding to different parts of the LH/hCG receptor mRNA were used.
Main Results:
- A specific mRNA binding protein, designated LRBP-1, was identified.
- LRBP-1 specifically binds to sequences within the LH/hCG receptor open reading frame.
- LRBP-1 RNA binding activity increased threefold during hCG-induced receptor down-regulation.
- LRBP-1 exhibited limited tissue expression.
Conclusions:
- LRBP-1 is the first identified LH/hCG receptor mRNA binding protein.
- LRBP-1 is a strong candidate for a trans-acting factor involved in regulating LH/hCG receptor mRNA stability.
- This finding provides insight into the molecular control of LH/hCG receptor expression.