Abstract

Loricrin gene expression is limited to terminally differentiating keratinocytes of stratified squamous epithelia. To define the regulatory elements that mediate the expression of the loricrin gene, we replaced the loricrin coding sequences from a 6.5-kilobase genomic fragment with the chloramphenicol acetyltransferase gene and transfected this construct into cultured mouse keratinocytes. High expression levels were observed in both undifferentiated as well as differentiating cells. Transgenic mice bearing a similar construct, but with beta-galactosidase as the reporter gene, corroborated these in vitro findings and showed tissue- and cell type-specific, but not differentiation-specific expression. Deletion analysis of the promoter region determined that sequences up to -60 base pairs from the start of transcription could be removed without significant loss of promoter activity. Within these proximal 60 base pairs is an evolutionarily conserved AP-1 element that is recognized by both purified c-Jun and AP-1 factors from keratinocytes in vitro. Mutation of this AP-1 site abolished the activity of the loricrin promoter. These studies show that elements directing expression of the loricrin gene to the stratified squamous epithelia are contained within a 6.5-kilobase genomic fragment, and those elements required to restrict expression to differentiated keratinocytes lie outside this region.

Highlights

  • Loricrin gene expression is limited to terminally differentiating keratinocytes of stratified squamous epithelia

  • Mutation of this AP-1 site abolished the activity ofthe loricrin promoter. These studies show that elements directing expression of the loricrin gene to the stratified squamous epithelia are contained within a 6.5·kilobase genomic fragment, and those elements required to restrict expression to differentiated keratinocytes lie outside this region

  • We show that loricrin transcription in vitro requires binding of protein factors to an AP-1 consensus site in the loricrin proximal promoter sequences, and that tissue-specific expression can be uncoupled from differentiation-specific expression both in vitro and in vwo

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Summary

Introduction

Loricrin gene expression is limited to terminally differentiating keratinocytes of stratified squamous epithelia. The Proximal Promoter of the Mouse Loricrin Gene Contains a Functional AP-l Element and Directs Keratinocyte-specific but Not Differentiation-specific Expression*

Results
Conclusion

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