Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
Mol Cell. 2018 Apr 19;70(2):297-311.e4. doi: 10.1016/j.molcel.2018.03.007. Epub 2018 Apr 5.
Gcn4 is a yeast transcriptional activator induced by amino acid starvation. ChIP-seq analysis revealed 546 genomic sites occupied by Gcn4 in starved cells, representing ∼30% of Gcn4-binding motifs. Surprisingly, only ∼40% of the bound sites are in promoters, of which only ∼60% activate transcription, indicating extensive negative control over Gcn4 function. Most of the remaining ∼300 Gcn4-bound sites are within coding sequences (CDSs), with ∼75 representing the only bound sites near Gcn4-induced genes. Many such unconventional sites map between divergent antisense and sub-genic sense transcripts induced within CDSs adjacent to induced TBP peaks, consistent with Gcn4 activation of cryptic bidirectional internal promoters. Mutational analysis confirms that Gcn4 sites within CDSs can activate sub-genic and full-length transcripts from the same or adjacent genes, showing that functional Gcn4 binding is not confined to promoters. Our results show that internal promoters can be regulated by an activator that functions at conventional 5'-positioned promoters.
Gcn4 是一种酵母转录激活因子，由氨基酸饥饿诱导。ChIP-seq 分析显示，在饥饿细胞中，Gcn4 占据了 546 个基因组位点，占 Gcn4 结合基序的约 30%。令人惊讶的是，只有约 40%的结合位点位于启动子中，其中只有约 60%能激活转录，这表明 Gcn4 功能受到广泛的负调控。其余约 300 个 Gcn4 结合位点中的大部分位于编码序列 (CDS) 内，其中约 75 个代表 Gcn4 诱导基因附近唯一的结合位点。许多这样的非常规位点位于相邻诱导 TBP 峰的 CDS 内的发散反义与亚基因有义转录本之间，这与 Gcn4 激活隐蔽的双向内部启动子一致。突变分析证实，CDS 内的 Gcn4 位点可以从同一或相邻基因的亚基因和全长转录本中激活，表明功能性 Gcn4 结合不受限于启动子。我们的结果表明，内部启动子可以被在常规 5'位置的启动子上发挥作用的激活剂调控。
