Epigenetic regulation of cardiac MHC gene locus

描述(由申请人提供)：心脏MHC基因(1和2)的相反调节在甲状腺状态改变、糖尿病、压力超负荷和发育过程中高度协调，但这种调节背后的机制尚不清楚。在以前的研究中，我们发现了一个自然存在的反义2RNA转录本，它始于2和1基因之间的基因间隔区(IGS)的中间，向上延伸到2MHC基因启动子区域，与2基因完全重叠。这种源于IGS的反义转录以前被认为是为了协调正常啮齿动物心脏中MHC基因的表达，以及对甲状腺状态改变、糖尿病和压力超负荷的反应。最近，通过链特异性RT-PCR对基因间RNA进行了更全面的分析，发现基因间RNA在正义方向上存在，该RNA转录到1MHC基本启动子区域并持续到1MHC基因(见图1)。这些结果(以及启动子报告实验的初步结果)有力地支持了IGS在啮齿动物心脏中双向转录活跃的新概念。下游链的转录向上游朝向2MHC基因，产生反义RNA：这一过程可能会干扰2基因的转录。上链转录，从1MHC基因TSS的上游~2kb开始，通过1个启动子进入1基因内部：这一过程可能会增强1基因的转录。因此，我们假设基因间双向转录控制相邻的1和2个MHC基因的协调相反调控。这项研究的目的是通过DNA甲基化、染色质重塑和组蛋白修饰等表观遗传机制，在改变心脏MHC基因座上相邻两个基因的表达的背景下，研究双向基因间转录的体内调节。出于比较的目的，作为我们理解该基因座上基因调控的方法的一部分，研究还将涉及心房和慢速骨骼肌。这些组织是独一无二的，因为前者主要表达1，而后者仅表达微量的1，其中2是主要的。因此，本研究将探索基因调控的新领域，并研究一种有趣的调控机制，涉及非编码基因间RNA，以及通过基因间双向转录对心脏MHC基因座位的表观遗传调控。

DESCRIPTION (provided by applicant): The antithetical regulation of the cardiac MHC genes (1 and 2) is highly coordinated in response to altered thyroid state, diabetes, pressure overload, and during development, yet the mechanism underlying this regulation is poorly understood. In previous studies, we discovered a naturally occurring antisense 2 RNA transcript that starts in the middle of the intergenic spacer (IGS) between the 2 and 1 genes and extends upstream to the 2MHC gene promoter region, fully overlapping the 2 gene. This antisense transcription originating from the IGS was previously proposed to coordinate cardiac MHC gene expression in normal rodent hearts and in response to altered thyroid state diabetes, and pressure overload. Recently, more comprehensive analyses of intergenic RNA via strand specific RT-PCR revealed the existence of intergenic RNA in the sense direction that is transcribed toward the 1MHC basic promoter region and continues through the 1MHC gene (see figure 1). These results (and preliminary results on promoter reporter assays) strongly support the novel concept that the IGS is transcriptionally active in both directions in rodent heart. Transcription of the lower strand, which proceeds upstream toward the 2MHC gene, produces antisense RNA: a process that may interfere with 2 gene transcription. Transcription of the upper strand, which starts from ~2kb upstream from the 1MHC gene TSS and proceeds through the 1 promoter to within the 1 gene: a process that may enhance 1 gene transcription. Thus, we hypothesize that the intergenic bidirectional transcription controls the coordinated antithetical regulation of adjacent 1 and 2 MHC genes. The goal of this proposed research is to examine the in vivo regulation of the bidirectional intergenic transcription in the context of altering the expression of the two adjacent genes on the cardiac MHC gene locus via an epigenetic mechanism which involves DNA methylation, chromatin remodeling and histone modification. For comparative purposes and as part of our approach to understanding the gene regulation on this locus, studies will also involve the atria and slow skeletal muscle. These tissues are unique in that the former expresses predominantly 1, while the latter expresses only traces of 1, with 2 being predominant. Consequently, this research will explore a new area of gene regulation and investigate an intriguing regulatory mechanism involving non-coding intergenic RNA, and epigenetic regulation of the cardiac MHC gene locus via bidirectional intergenic transcription.