Regulatory regions of DNA, which control gene expression, influence the intensity of the transcription and are composed of promoters, enhancers, silencers and insulators. An example of tissue-specific gene expression can be observed in the mammary gland, which expresses milk proteins that are divided into caseins and whey proteins. Regulation of milk protein gene expression is very important, since they are only expressed during lactation and are depended on lactogenic hormones.
We sequenced the κ-casein promoter region of four Linnaeus's two-toed sloths (Choloepus didactylus) individuals and conducted an alignment analysis. The alignment results showed, as anticipated, a considerable degree of sequence conservation within the same species, while exhibiting minimal polymorphic regions. We performed a comparative analysis of κ-casein promoter region sequences across different mammalian species with the intention of interspecies comparison. This analysis revealed a remarkable degree of similarity, suggesting the presence of highly conserved sequence motifs. However, certain regions showed variations, mainly insertions/deletions. We further extended the analysis to compare transcription factor binding sites, revealing that interspecies differences indicate that considerable variability in promoter structures allow tissue-specific expression.
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