Complete nucleotide sequence of the chicken chromosomal ovalbumin gene and its biological significance

Abstract

The nucleotide sequence of the entire chicken chromosomal ovalbumin gene was determined. The gene is 7564 nucleotides in length to code for a mature MRNA of 1872 nucleotides. Comparison of the sequence at the 5''-terminal region of the gene with that reported by others revealed multiple polymorphic nucleotides in the structural, intervening and flanking DNA sequences. Some of the polymorphic sites occur at positions very close to splice junctions or the eukaryotic promoter sequence, yet apparently have little or no effect on the expression of this gene. The heptanucleotide promoter sequence TATATAT present in the 5''-flanking region of the ovulbumin gene does not occur within the confines of the gene. Multiple Hogness box sequences similar to those found in other eukaryotic genes were delineated within the boundaries of the gene. These internal Hogness box sequences are not used for transcription initiation. The hexanucleotide sequence AATAAA common to all eukaryotic mRNA at the 3''-untranslated region occurs 7 additional times within the ovalbumin gene. These sites are not used for transcription termination or polyadenylation. Although these sequences may play important roles in the initiation or termination of gene transcripts as well as polyadenylation of the transcripts, the specificity for such biological functions must not reside within these sequences alone. Sequences complementary to the highly conserved rat U1 small nuclear RNA were found throughout the gene. Many of these regions of complementarity occur in the structural sequences. If the small nuclear RNA does play a role in splicing, the specificity must be provided also by other as yet undefined components.