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Molecular cloning of a new human insulin-like growth factor binding protein
M C Kiefer1, R S Ioh, D M Bauer
1Chiron Corporation, Emeryville, CA 94608.
Abstract:
We have cloned a new insulin-like growth factor's binding protein (IGFBP) from a human osteosarcoma cDNA library. Two conserved regions in the COOH-terminal third of the five known human IGFBPs were used to design primers and to perform polymerase chain reaction (PCR) with osteosarcoma cDNA as a template. One of the eight PCR products encoded a unique IGFBP sequence. The DNA sequence was used to synthesize probes to screen an osteosarcoma cDNA library and isolate full length cDNA clones. The amino acid sequence was deduced from one of them. It contains two possible signal peptidase cleavage sites yielding a mature molecule of 257 or 252 amino acids, and 18 cysteines in identical positions to the other IGFBPs. The most pronounced homology exists with human IGFBP-3 (50% in the NH2- and 45% in the COOH-terminal region).
Insights
Researchers cloned a novel insulin-like growth factor-binding protein (IGFBP) from human osteosarcoma cells. This new IGFBP shows significant homology to IGFBP-3, suggesting a role in bone cancer progression.
Area of Science:
- Molecular Biology
- Biochemistry
- Oncology
Background:
- Insulin-like growth factor-binding proteins (IGFBPs) play crucial roles in regulating IGF bioavailability.
- Osteosarcoma is a primary bone cancer with complex molecular underpinnings.
- Understanding novel IGFBP functions is vital for cancer research.
Purpose of the Study:
- To identify and characterize a new IGFBP from human osteosarcoma.
- To determine the sequence and structural features of the novel IGFBP.
- To assess the homology of the new IGFBP to known IGFBP family members.
Main Methods:
- Polymerase chain reaction (PCR) using degenerate primers based on conserved IGFBP regions.
- Screening of a human osteosarcoma cDNA library.
- DNA sequencing and amino acid sequence deduction.
- Sequence homology analysis.
Main Results:
- A unique IGFBP sequence was identified from PCR products.
- Full-length cDNA clones of the novel IGFBP were isolated.
- The deduced amino acid sequence revealed two potential signal peptidase cleavage sites.
- The mature protein consists of 257 or 252 amino acids with 18 conserved cysteines.
- Highest homology was observed with human IGFBP-3 (50% NH2-terminal, 45% COOH-terminal).
Conclusions:
- A novel human IGFBP has been successfully cloned and sequenced.
- The new IGFBP shares significant structural similarities with IGFBP-3.
- Further studies are warranted to elucidate the specific functions of this novel IGFBP in osteosarcoma.