RNA polymerase II is a glycoprotein. Modification of the COOH-terminal domain by O-GlcNAc.
RNA polymerase II is a glycoprotein. Modification of the COOH-terminal domain by O-GlcNAc.
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DOI：
10.1016/s0021-9258(18)82216-5
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发表时间：
1993-05
期刊：
影响因子：
--
通讯作者：
William G. Kelly;M. Dahmus;G. Hart
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文献类型：
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作者：
William G. Kelly;M. Dahmus;G. Hart
哺乳动物RNA聚合酶II(RNAP II)的最大亚基在其羧基末端含有一个不寻常的结构域，由52个串联重复序列组成，其共有序列为Tyr-Ser-Pro-Thr-Ser-Pro-Ser。这个结构域被称为COOH-末端结构域(CTD)，对于活性是必不可少的，并且在从预引发复合体组装到延伸的过渡过程中被广泛的磷酸化(1)。事实上，CTD的磷酸化可能在这一转变中发挥重要的调节作用。我们在这里表明，CTD也被一种新形式的蛋白质糖基化修饰，O-GlcNAc。这种修饰已经在许多转录因子和其他核和胞质蛋白上被发现(2)。用反相高效液相色谱分离纯化CTD蛋白水解物得到的糖肽，并进行序列测定。这些实验的结果表明，糖基化发生在整个CTD的多个位置，类似于这个结构域的磷酸化。然而，在磷酸化形式的酶上检测不到碳水化合物。这一观察结果与磷酸化和糖基化是互斥修饰的观点是一致的。因此，RNAP II的CTD似乎存在三种不同的构象状态：未修饰的、磷酸化的和糖基化的。CTD的差异修饰可能在RNA聚合酶II转录的基因表达调控中发挥重要作用。
The largest subunit of mammalian RNA polymerase II (RNAP II) contains at its carboxyl terminus an unusual domain consisting of 52 tandem repeats of the consensus sequence Tyr-Ser-Pro-Thr-Ser-Pro-Ser. This domain, designated the COOH-terminal domain (CTD), is essential for viability and is extensively phosphorylated during the transition from preinitiation complex assembly to elongation (1). Indeed, phosphorylation of the CTD may play an important regulatory role in this transition. We show here that the CTD is also modified by a novel form of protein glycosylation, O-GlcNAc. This modification has been found on numerous transcription factors and other nuclear and cytosolic proteins (2). Glycopeptides obtained by proteolytic digestion of the CTD were purified by reverse-phase high performance liquid chromatography and sequenced. Results from such experiments suggest that glycosylation occurs at multiple sites throughout the CTD, similar to the phosphorylation of this domain. The carbohydrate, however, is not detectable on the phosphorylated form of the enzyme. This observation is consistent with the idea that phosphorylation and glycosylation are mutually exclusive modifications. The CTD of RNAP II, therefore, appears to exist in three distinct conformational states: unmodified, phosphorylated, and glycosylated. The differential modification of the CTD may play an important role in the regulated expression of genes transcribed by RNA polymerase II.