Sequence-specific DNA-binding proteins which interact with (G + C)-rich sequences flanking the chicken c-myc gene

The interaction of nuclear sequence-specific DNA-binding proteins from definitive chicken erythrocytes, thymus and proliferating transformed erythroid precursor (HD3) cells with the 700-base-pair (700-bp) DNA 5'-flanking region of the chicken c-myc gene was investigated by in vitro footprint analysis. The major HD3 protein-binding activity binds to a site (site V) 200 bp upstream from the 'cap' site but, after further fractionation, a second distinct binding activity is detected to a site (site VIII) which contains both the 'CAAT' and 'SP1-binding' consensus sequences. Protein from thymus and erythrocyte cells which express c-myc at lower levels, bind to seven and eight sites respectively. In common with HD3 cell protein, they both bind to site VIII and, although binding to the sequence at site V is also detected, the footprint protection pattern is sufficiently different (site V') to suggest the involvement of different proteins in terminally differentiated and proliferating cells. The DNA-binding activities were partially fractionated by high-performance liquid chromatography gel filtration and include an erythrocyte-specific protein which binds to a c-myc gene poly(dG) homopolymer sequence similar to that found upstream of the chicken beta A-globin gene.     

Nuclear factor 1 is a component of the nuclear matrix

Chicken histone H5 is an H1-like linker histone that is expressed only in nucleated erythrocytes. The histone H5 promoter has binding sites for Sp1 (a high affinity site) and UPE-binding protein, while the 3′ erythroid-specific enhancer has binding sites for Sp1 (one moderate and three weak affinity), GATA-1, and NF1. In this study we investigated whether trans-acting factors that bind to the chicken histone H5 promoter or enhancer are associated with adult chicken immature and mature erythrocyte nuclear matrices. We show that NF1, but not Sp1, GATA-1, or UPE-binding protein, is associated with the internal nuclear matrices of these erythroid cells. Further, we found that a subset of the NF1 family of proteins is bound to the mature erythrocyte nuclear matrix. These results suggest that in chicken erythrocytes NF1 may mediate an interaction between the histone H5 enhancer and the erythroid internal nuclear matrix. NF1 was also present in the internal nuclear matrices of chicken liver and trout liver. The observations of this study provide evidence that NF1 may have a role in a variety of cell types in targeting specific DNA sequences to the nuclear matrix. © 1994 Wiley-Liss, Inc.     

EGF对EGFR基因和c-fos、c-myc原癌基因DNA结合蛋白质的影响

基因转录调控作用是EGF的细胞核内作用之一,而序列特异的DNA结合蛋白质与基因转录的调控密切相关。本文以C_3H小鼠胚胎正常成纤维细胞C_3H_(10)T_(1/2)C18(简称NC_3H_(10))株及其氚标记脱氧胸苷(~3H-TdR)恶性转化的细胞株(简称TC_3H_(10))为对象,我们研究了EGF作用下,核内蛋白质与EGFR基因和c-fos、c-myc二种原癌基因的结合状态。研究发现,EGF的持续作用可使EGFR基因的特异结合蛋白质P120、c-fos基因的特异结合蛋白质P80、以及c-myc基因的特异结合蛋白质P125等明显增加。这些结果提示基因的特异结合蛋白质可能与EGF对基因转录的调控密切相关。上述结果尚未见到国内外同类报道。