THE NONSPECIFIC DNA-BINDING AND DNA-BENDING PROTEINS HMG1 AND HMG2 PROMOTE THE ASSEMBLY OF COMPLEX NUCLEOPROTEIN STRUCTURES
THE NONSPECIFIC DNA-BINDING AND DNA-BENDING PROTEINS HMG1 AND HMG2 PROMOTE THE ASSEMBLY OF COMPLEX NUCLEOPROTEIN STRUCTURES
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DOI：
10.1101/gad.7.8.1521
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发表时间：
1993-08-01
影响因子：
10.5
通讯作者：
JOHNSON, RC
中科院分区：
文献类型：
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作者：
PAULL, TT;HAYKINSON, MJ;JOHNSON, RC
哺乳动物高迁移率族蛋白HMG 1和HMG 2是丰富的染色质相关蛋白，其细胞功能尚不清楚。在这项研究中，我们表明，这些蛋白质可以取代原核生物的DNA弯曲蛋白HU在促进组装的Hin invertasome，中间结构在Hin介导的位点特异性DNA倒位。该复合物的形成需要Hin重组酶、Fis蛋白和三个顺式作用DNA位点的组装，从而需要插入DNA片段的成环。转化酶体组装强烈刺激HU或HMG蛋白质时，这些片段之一是短于104 bp。通过使用连接酶介导的环化分析，我们证明HMG 1和HMG 2可以非常有效地弯曲DNA，形成小至66 bp的环，甚至在高HMG蛋白浓度下形成59 bp的环。在转化酶体组装和环化测定中，与在HU蛋白存在下有活性的底物相比，在HMG 1存在下有活性的底物含有少一个DNA螺旋转角。通过部分蛋白水解消化产生的HMG 1的不同结构域的分析表明，DNA结合结构域B足以进行弯曲和转化体组装。我们认为HMG 1和HMG 2的一个重要生物学功能是通过促进DNA的灵活性来促进顺式作用蛋白之间的合作相互作用。HMG 1和HMG 2在染色质结构中的一般作用也由它们将DNA双链体包裹成高度紧凑形式的能力提出。
The mammalian high mobility group proteins HMG1 and HMG2 are abundant, chromatin-associated proteins whose cellular function is not known. In this study we show that these proteins can substitute for the prokaryotic DNA-bending protein HU in promoting the assembly of the Hin invertasome, an intermediate structure in Hin-mediated site-specific DNA inversion. Formation of this complex requires the assembly of the Hin recombinase, the Fis protein, and three cis-acting DNA sites, necessitating the looping of intervening DNA segments. Invertasome assembly is strongly stimulated by HU or HMG proteins when one of these segments is shorter than 104 bp. By use of ligase-mediated circularization assays, we demonstrate that HMG1 and HMG2 can bend DNA extremely efficiently, forming circles as small as 66 bp, and even 59-bp circles at high HMG protein concentrations. In both invertasome assembly and circularization assays, substrates active in the presence of HMG1 contain one less helical turn of DNA compared with substrates active in the presence of HU protein. Analysis of different domains of HMG1 generated by partial proteolytic digestion indicate that DNA-binding domain B is sufficient for both bending and invertasome assembly. We suggest that an important biological function of HMG1 and HMG2 is to facilitate cooperative interactions between cis-acting proteins by promoting DNA flexibility. A general role for HMG1 and HMG2 in chromatin structure is also suggested by their ability to wrap DNA duplexes into highly compact forms.