Jha Pravin K, Khan Mohd Imran, Mishra Anshul, Das Pradeep, Sinha Kislay K
Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Hajipur, Bihar, India.
Molecular Biology Division, Rajendra Memorial Research Institute of Medical Sciences, Patna, Bihar, India.
PLoS One. 2017 May 9;12(5):e0177372. doi: 10.1371/journal.pone.0177372. eCollection 2017.
Histone post-translational modifications (PTMs) such as acetylation and methylation are known to affect chromatin higher order structures. Primary targets of these modifications include basic residues present at N-terminus tail region of core histones. Four histone acetyltransferase (HAT) genes have been identified in trypanosomatids. HAT1, HAT3 and HAT4 of Leishmania donovani have been partially characterized. However, there is no report about HAT2 of Leishmania donovani. Lysine residues present on the N-terminal tail of Leishmania donovani histone H4 are conserved in other trypanosomatids and humans. PTMs of lysines modulate various functions at chromatin level. The four histone acetyltransferases encoded in Leishmania genome were over-expressed to analyse their functional activity. All four HATs were found actively acetylating core histones H3/H4. Similar to L. donovani HAT3 and HAT4, HAT2 was found to be a member of MYST family protein and have SAS2 type domain. Over-expression of HAT2 significantly increases acetylation of H4K4. To analyse the effect of HAT2 over-expression on chromatin accessibility, micrococcal nuclease digestion assay was performed. MNase digestion resulted in a higher proportion of the mononucleosomes and dinucleosomes in HAT2 over-expressing cells as compared to WT L. donovani cells. Acetylation of lysine-4 neutralizes the amino terminal region of histone H4. This weakens its interaction with neighbouring nucleosomes and the linker DNA. HAT2 over-expression in L. donovani resulted in highly accessible chromatin suggesting chromatin decondensation. HAT2 may have an important role to play in global regulation of transcription in L. donovani. Better understanding of these epigenetic determinants of parasite would help in designing novel therapeutic strategies.
已知组蛋白翻译后修饰（PTM）如乙酰化和甲基化会影响染色质的高级结构。这些修饰的主要靶点包括核心组蛋白N端尾部区域的碱性残基。在锥虫中已鉴定出四个组蛋白乙酰转移酶（HAT）基因。杜氏利什曼原虫的HAT1、HAT3和HAT4已得到部分表征。然而，关于杜氏利什曼原虫HAT2尚无报道。杜氏利什曼原虫组蛋白H4 N端尾部的赖氨酸残基在其他锥虫和人类中是保守的。赖氨酸的PTM在染色质水平调节多种功能。杜氏利什曼原虫基因组中编码的四种组蛋白乙酰转移酶被过表达以分析其功能活性。发现所有四种HAT都能使核心组蛋白H3/H4发生乙酰化。与杜氏利什曼原虫HAT3和HAT4类似，发现HAT2是MYST家族蛋白的成员并具有SAS2型结构域。HAT2的过表达显著增加了H4K4的乙酰化。为了分析HAT2过表达对染色质可及性的影响，进行了微球菌核酸酶消化试验。与野生型杜氏利什曼原虫细胞相比，微球菌核酸酶消化导致HAT2过表达细胞中单核小体和双核小体的比例更高。赖氨酸-4的乙酰化中和了组蛋白H4的氨基末端区域。这削弱了它与相邻核小体和连接DNA的相互作用。杜氏利什曼原虫中HAT2的过表达导致染色质高度可及，表明染色质解聚。HAT2可能在杜氏利什曼原虫转录的全局调控中发挥重要作用。更好地了解寄生虫的这些表观遗传决定因素将有助于设计新的治疗策略。
