Structural analysis of the gene encoding human gastrin: the large intron contains an Alu sequence

Area of Science:

• Molecular Biology
• Genetics
• Human Physiology

Background:

• Gastrin plays a crucial role in regulating gastric acid secretion.
• Understanding the human gastrin gene structure is essential for studying its expression and regulation.

Purpose of the Study:

• To isolate and characterize the human gastrin gene.
• To determine the gene's structural organization, including exons and introns.
• To identify regulatory elements within the gene sequence.

Main Methods:

• Isolation of the human gastrin gene from a genomic library using a human gastrin cDNA clone as a probe.
• Nucleotide sequence analysis of the gene.
• S1 nuclease protection mapping to identify the transcription initiation site.

Main Results:

• The human gastrin gene is approximately 4.0 kilobase pairs long, comprising three exons and two introns.
• A 130-base-pair intron interrupts the coding region, and a 3.0-kilobase-pair intron is in the 5' untranslated region.
• Key regulatory sequences including a TATA-like element, CAT box, and poly(A)-addition signal were identified. The aspartic acid codon at position 71 of preprogastrin is interrupted by the small intron. A 300-nucleotide sequence homologous to the human Alu-type sequence was found in the 3' region of the large intron.

Conclusions:

• The isolated human gastrin gene structure provides a basis for further investigation into gastrin gene expression.
• Identification of regulatory elements offers insights into transcriptional control mechanisms.
• The presence of an Alu-type sequence suggests potential roles in gene evolution or regulation.