DNA sequence comparison of the regulatory signals at the 5' end of the mouse and chick alpha 2 type I collagen genes

Abstract

We have isolated a DNA segment that contains the presumptive transcriptional and translational control signals located at the 5' end of the mouse alpha 2(I) collagen gene. The DNA sequence of the first exon of this gene and of 400 base pairs preceding the start of transcription was compared with an analogous sequence in the chick alpha 2(I) collagen gene. The most striking similarity is a block of 68 nucleotides surrounding the translation initiation site which is perfectly conserved except for four contiguous nucleotides in the middle of the conserved sequence. These four nonconserved bases lie between the arms of a perfect inverted repeat with nine nucleotides in each arm. The very high degree of sequence conservation of this segment suggests that both the inverted repeat and the rest of the perfectly conserved sequence have a regulatory role, possibly in translation. The segment preceding the transcription start shows blocks of similarities interspersed with dissimilar sequences. The conserved sequences include the TATA box, CAT box, a G/C rich sequence around -110, a segment that contains almost exclusively pyrimidines on one strand and is sensitive to endonuclease S1 in both promoters, and several other segments that extend to 350 base pairs preceding the start of transcription. Although the distances between these regions of similarity and the TATA box are not the same in the two promoters, we believe the conserved sequences play a role in the transcriptional activation of this gene.