Abstract
Recently we have isolated a large number of chicken myosin or myosin-like heavy chain genes. Seven of these genes were placed into a subset based upon their hybridization patterns. In the present study, the sequence of the 5' end of one of the myosin heavy chain (MHC) genes, N127, was determined and compared with the 5' end sequences of the other six MHC genes in the subset. The comparison revealed that the three exons encoding the amino termini of the protein are highly conserved. The sequence analysis shows that a localized correction event occurred in and around a domain of the nucleotide-binding site, as the exon encoding this site and the preceding intron are very highly conserved among the seven genes. The sequence of the promoter and 5'-untranslated region of N127 is presented. The analogous regions for N124 and N125 have now been sequenced and are also presented. As is the case for all the other known MHC genes, the 5'-untranslated regions are split by large introns. The promoter and 5'-untranslated regions are compared with two previously characterized chicken MHC genes (N116 and N118) to determine the sequence similarities and differences that might underlie the differential expression of the family's members. To confirm and extend previously published results of the expression of these genes, transcript-specific probes generated from the 5' region of six of the seven genes were used to determine in which muscle(s) the corresponding mRNAs were present. The data show that despite the very close structural homologies, each of the genes for which a unique probe could be prepared exhibits a unique pattern of expression.
Highlights
With the 5‘ end sequences of the other six myosin heavy chain (MHC) genes genes remain largely obscure
503467. $Supported by National Institutes of Health TrainingGrant promoters, so that the similarities and differences among these sequences can be catalogued and hopefully correlated with the genes’ expression. We have addressed these problems by focusing our attention on a group of seven chicken MHC genes
The results presented here show that the organization of the seven chicken MHC genes at the5’ ends is conserved
Summary
The procedures used in isolating and mappingthe genomic clone have been described previously[5]. The hybridization using the 423-base pair PstI/Sau3A fragment first approximately 36 nucleotides of exon three comprise the of N116, which was shown previously to encode the 5' end of rest of the 5"untranslated region, and it is these sequences an adult MHC gene[43]. Mostof the nucleotide changes in the translatedregion occur at the silent site (third position) in the codons and result in the conservation of the amino acid. Comparison of the Genes’ Transcription-As mentioned above, the transcriptional patternsof other genes within the subset of seven have been determined previously using transcript-specific probes [5, 6, 43] and various methodologies We thought it useful, based on the above analyses for N127, O.
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