Related Experiment Videos
Genomic organization of the alpha chain of the human C4b-binding protein gene
T Aso1, S Okamura, T Matsuguchi
1First Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Insights
Researchers elucidated the genetic structure of the human C4b-binding protein alpha chain (C4bp alpha), revealing a unique split short consensus repeat (SCR) encoded across multiple exons. This finding enhances understanding of complement regulation and C4bp synthesis. Keywords: C4b-binding protein, complement activation, gene structure, short consensus repeats.
Area of Science:
- Molecular Biology
- Immunology
- Genetics
Background:
- C4b-binding protein (C4bp) is a key regulator of complement activation (RCA) in serum.
- C4bp comprises alpha and beta polypeptide chains; the alpha chain contains eight short consensus repeats (SCRs).
- Human C4bp functions as an acute-phase reactant, suggesting complex regulatory mechanisms for its synthesis.
Purpose of the Study:
- To investigate the genetic basis of the short consensus repeats (SCRs) within the C4bp alpha chain.
- To elucidate the regulatory mechanisms governing C4b-binding protein synthesis at the genomic level.
Main Methods:
- Isolation of six genomic DNA clones encompassing the entire human C4bp alpha gene.
- Sequencing of the gene, including its 12 exons and approximately 40 kb span.
- Analysis of the 5' flanking region up to 380 bases upstream of the transcription initiation site.
Main Results:
- The human C4bp alpha gene comprises 12 exons.
- Each SCR is encoded by a single exon, with the exception of SCR II, which is split across two exons.
- Identification of potential transcription factor binding sites in the 5' flanking region.
Conclusions:
- Demonstrates a split SCR at the genomic level for human C4bp alpha, a novel finding.
- Provides insights into the genetic architecture influencing C4bp regulation.
- Suggests potential transcriptional control mechanisms involving identified transcription factor binding sites.
Abstract:
C4b-binding protein (C4bp) is a serum glycoprotein that is one of the regulators of the complement activation (RCA) family. This protein is composed of structurally related 70-kDa (alpha chain) and 45-kDa (beta chain) polypeptides. The alpha chain of C4bp (C4bp alpha) consists of eight short consensus repeats (SCR), which constitute the amino-terminal 491 residues. Human C4bp is also one of the acute-phase reactants. In order to clarify the genetic basis of the SCR and to understand the regulatory mechanisms of C4bp synthesis, we isolated 6 genomic DNA clones covering all of the human C4bp alpha gene. This gene consists of 12 exons and spans about 40 kb. Each of the SCRs is encoded by a single exon, except for the second SCR (SCR II), which is encoded by two separate exons, demonstrating that human C4bp alpha has a split SCR at the genomic level. The 5' flanking region was sequenced up to 380 bases upstream from the putative transcription initiation site. Several possible binding sites for transcription factors were identified.