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Mapping of steroid 21-hydroxylase genes adjacent to complement component C4 genes in HLA, the major
Insights
Researchers identified the steroid 21-hydroxylase gene within the human major histocompatibility complex. This gene is crucial for adrenal function and is located near complement component genes.
Area of Science:
- Human genetics
- Molecular biology
- Biochemistry
Background:
- The human major histocompatibility complex (HLA) contains genes for complement components.
- Previous studies aligned cosmid inserts containing complement C4A and C4B genes within the HLA complex.
Purpose of the Study:
- To identify a gene within the HLA complex that is expressed in the adrenal gland.
- To characterize the gene located 3' to the C4A and C4B complement genes.
Main Methods:
- Hybridization of cosmid inserts with human adrenal mRNA.
- DNA sequencing of a 430-base region.
- Comparison with published cDNA and peptide sequences of cytochrome P-450 21-hydroxylase.
- Gene mapping using synthetic oligonucleotides.
Main Results:
- A gene expressed in the adrenal gland was identified within the HLA complex.
- The gene, located 1.5 kb 3' of C4A and C4B genes, codes for human steroid 21-hydroxylase (EC 1.14.99.10).
- The gene's mRNA is 2.4 kb, and its genomic DNA is 4.5 kb.
Conclusions:
- The steroid 21-hydroxylase gene is located within the human major histocompatibility complex.
- This finding provides insights into the genetic organization and regulation of steroidogenesis and immune function.
Abstract:
The genes for four components (C) of complement in the human major histocompatibility complex (HLA) have been aligned previously in a series of overlapping cosmid cloned inserts. Those inserts, which contained the two C4 genes C4A and C4B, hybridized with human adrenal mRNA, indicating that they contain a gene expressed in the adrenal. The mRNA fraction of 2.4 kilobases (kb) hybridizes with genomic DNA of 4.5 kb, which is duplicated and lies about 1.5 kb 3' of both the C4A and the C4B complement genes. Sequencing of a 430-base section and comparison with the published cDNA sequence of bovine cytochrome P-450 21-hydroxylase, peptide sequences of porcine 21-hydroxylase, and a cDNA sequence of a rat liver cytochrome P-450 identified the gene as coding for human steroid 21-hydroxylase [steroid,hydrogen-donor:oxygen oxidoreductase (21-hydroxylating), EC 1.14.99.10]. Mapping of the gene was helped by use of a synthetic oligonucleotide based on the bovine cDNA sequence.