DNA distortion and multimerization: novel functions of the glutamine-rich domain of GAGA factor.
GAGA factor (GAF) is an essential protein in Drosophila melanogaster, important for the transcriptional regulation of numerous genes. The effect of GAF on chromatin structure and promoter function has been the subject of much attention, yet little is known of the actual mechanism and the specific contributions of individual GAF domains to its function. The DNA-binding activity of GAF, as specified by the single zinc finger binding domain (Zn), has been examined in some detail; however, the functions of the POZ/BTB and glutamine domain (Q) remain poorly understood. Here, we report three separate activities of the Q domain of GAF; promoter distortion, single-strand binding, and multimerization. In vitro, GAF binding to the hsp70 promoter produces extended DNase I protection and KMnO4 hypersensitivity. These activities require both the Zn domain and Q domain of GAF, and appear independent of the POZ/BTB domain. GAF also has a single-stranded DNA binding affinity, as does the Q-rich region alone. GAF forms multimers both in vitro and in vivo, and the Q domain itself forms multimers. Protein-protein interactions mediated by the Q domain may, therefore, be at least partially responsible for the multimerization capabilities of GAF. We discuss these findings in the context of their possible function in GAF mediated transcriptional regulation.
Wilkins
R C
RC
Section of Genetics and Development, Cornell University, Ithaca NY 14853, USA.
Lis
J T
JT
D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D005973:Glutamine / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012996:Solutions; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015032:Zinc
D002352:Carrier Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D058619:Maltose-Binding Proteins; D011993:Recombinant Fusion Proteins; D012996:Solutions; D014157:Transcription Factors; C063460:Trl protein, Drosophila; D005973:Glutamine; D004247:DNA; D015032:Zinc