Affiliation:
1. Biology Department, Johns Hopkins University, Baltimore, Maryland 21218.
Abstract
A cis-acting regulatory element within the gag gene of avian retroviruses has been localized by deletion analysis, and sites of protein interaction have been studied by DNase I footprinting. Unidirectional deletions were made from both the 5' and 3' ends of a 656-base-pair fragment of the gag gene of Fujinami sarcoma virus. These deletion mutants were tested for enhancer activity in a chloramphenicol acetyltransferase transient expression assay. A sharp 5' boundary for enhancer activity was observed between 776 and 786 nucleotides downstream from the transcription initiation site. In contrast, deletion from the 3' side resulted in a gradual loss of enhancer activity, reaching a near basal level of activity by nucleotide 868. Internal deletion of 76 nucleotides just downstream of the 5' boundary abolished enhancement. Mutagenesis of a consensus enhancer core sequence (GTGGTTTG) showed that this sequence was not necessary for enhancer activity in our transient assays. DNase I footprinting with both a highly purified enhancer-binding protein from rat liver (EBP20) and a partially purified chicken liver nuclear extract showed specific protection of nucleotides 813 to 872 within the localized enhancer region. Footprinting of unidirectional deletion mutants that had lost activity indicated that this binding was not sufficient to confer enhancement.
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
Cited by
35 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献