Palvimo J, Mäenpää P H
Department of Biochemistry, University of Kuopio, Finland.
Biochim Biophys Acta. 1988 Jan 29;952(2):172-80. doi: 10.1016/0167-4838(88)90113-6.
We have used affinity chromatography to study the effects of phosphorylation of calf thymus high-mobility-group proteins HMG 14 and HMG 17 on their binding properties towards calf thymus single- and double-stranded DNA and histone H1. Without in vitro phosphorylation, HMG 14 and HMG 17 eluted from double-stranded DNA-columns at 200 mM NaCl. HMG 14 was released from single-stranded DNA-column at 300 mM NaCl and from H1-column at 130 mM NaCl, whereas the corresponding values for HMG 17 were 230 mM and 20 mM, respectively. Phosphorylation of HMG 14 and HMG 17 by cAMP-dependent protein kinase (A-kinase) decreased markedly their affinity (270 mM and 200 mM NaCl, respectively) for single-stranded DNA, whereas HMG 14 phosphorylated by nuclear protein kinase II (NII-kinase) eluted only slightly (290 mM NaCl) ahead of the unphosphorylated protein. HMG 14 phosphorylated by both A-kinase and NII-kinase eluted from double-stranded DNA-columns almost identically (190 mM NaCl) with the unphosphorylated protein. Interestingly, phosphorylation of HMG 14 by NII-kinase increased considerably its affinity for histone H1 and the phosphorylated protein eluted at 200 mM NaCl. Phosphorylation of HMG 14 by A-kinase did not alter its interaction towards histone H1. These results indicate that modification of HMG 14 by phosphorylation at specific sites may have profound effects on its binding properties towards DNA and histone H1, and that HMG 17 has much weaker affinity for single-stranded DNA and histone H1 than HMG 14.
我们利用亲和层析法研究了小牛胸腺高迁移率族蛋白HMG 14和HMG 17的磷酸化对其与小牛胸腺单链和双链DNA以及组蛋白H1结合特性的影响。在无体外磷酸化的情况下，HMG 14和HMG 17在200 mM NaCl浓度下从双链DNA柱上洗脱下来。HMG 14在300 mM NaCl浓度下从单链DNA柱上洗脱下来，在130 mM NaCl浓度下从H1柱上洗脱下来，而HMG 17的相应值分别为230 mM和20 mM。由cAMP依赖性蛋白激酶（A激酶）介导的HMG 14和HMG 17磷酸化显著降低了它们对单链DNA的亲和力（分别为270 mM和200 mM NaCl），而由核蛋白激酶II（NII激酶）磷酸化的HMG 14仅比未磷酸化的蛋白稍早一点（290 mM NaCl）洗脱下来。由A激酶和NII激酶磷酸化的HMG 14从双链DNA柱上洗脱的情况几乎与未磷酸化的蛋白相同（190 mM NaCl）。有趣的是，由NII激酶磷酸化的HMG 14对组蛋白H1的亲和力显著增加，磷酸化蛋白在200 mM NaCl浓度下洗脱下来。由A激酶磷酸化的HMG 14对组蛋白H1的相互作用没有改变。这些结果表明，在特定位点进行磷酸化对HMG 14的修饰可能对其与DNA和组蛋白H1的结合特性产生深远影响，并且HMG 17对单链DNA和组蛋白H1的亲和力比HMG 14弱得多。
