O'Brien T, Wilkins R C, Giardina C, Lis J T
Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA.
Genes Dev. 1995 May 1;9(9):1098-110. doi: 10.1101/gad.9.9.1098.
GAGA protein binds specific CT.GA-rich DNA sequences in vitro, and many of these sequences are required for transcription in vivo. GAGA protein has been implicated in the transcription of numerous Drosophila genes, including hsp70, hsp26, actin 5C, and Ubx. Here, we examine the in vivo distribution of GAGA protein on a number of Drosophila genes that do and do not have CT-rich sequences by use of a UV cross-linking technique. Prior to heat shock, GAGA protein is associated with the promoter regions of the uninduced hsp70 and hsp26 genes. Upon heat shock induction, GAGA protein is recruited to their transcription units with its distribution coincident with that of RNA polymerase II. The recruitment of GAGA protein to the hsp70 gene after an instantaneous heat shock occurs in a 5' to 3' manner with kinetics similar to RNA polymerase. GAGA protein has been shown to disrupt nucleosome both in vivo and in vitro. We propose that GAGA protein may function in vivo both by binding constitutively to its high-affinity binding sites and by spreading through the induced gene opening the chromatin structure allowing polymerase to elongate efficiently.
GAGA蛋白在体外能结合富含CT.GA的特定DNA序列，其中许多序列在体内转录过程中是必需的。GAGA蛋白与众多果蝇基因的转录有关，包括热休克蛋白70（hsp70）、热休克蛋白26（hsp26）、肌动蛋白5C（actin 5C）和超双胸蛋白（Ubx）。在此，我们通过紫外线交联技术研究了GAGA蛋白在果蝇一些含有和不含有富含CT序列的基因上的体内分布情况。在热休克之前，GAGA蛋白与未诱导的hsp70和hsp26基因的启动子区域相关联。热休克诱导后，GAGA蛋白被募集到它们的转录单元，其分布与RNA聚合酶II的分布一致。瞬时热休克后，GAGA蛋白以5'到3'的方式被募集到hsp70基因，其动力学与RNA聚合酶相似。GAGA蛋白已被证明在体内和体外都能破坏核小体。我们提出，GAGA蛋白在体内可能通过以下两种方式发挥作用：一是持续结合其高亲和力结合位点，二是通过诱导基因扩散，打开染色质结构，使聚合酶能够有效地延伸。
