Epigenetic regulation of cardiac MHC gene locus

描述（由申请人提供）：心脏MHC基因（1和2）的对立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，但这种调节的机制尚不清楚。在以前的研究中，我们发现了一种天然存在的反义2 RNA转录物，它起始于2和1基因之间的基因间间隔区（IGS）的中间，并向上游延伸到2 MHC基因启动子区，与2基因完全重叠。这种源自IGS的反义转录先前被提出来协调正常啮齿动物心脏中的心脏MHC基因表达，并响应于改变的甲状腺状态、糖尿病和压力超负荷。最近，通过链特异性RT-PCR对基因间RNA进行了更全面的分析，结果显示存在有义方向的基因间RNA，该基因间RNA向1 MHC基本启动子区域转录，并继续通过1 MHC基因（见图1）。这些结果（和启动子报告基因测定的初步结果）强烈支持IGS在啮齿动物心脏中在两个方向上都具有转录活性的新概念。下链的转录向上游向2 MHC基因进行，产生反义RNA：这一过程可能会干扰2基因的转录。上链的转录，从1 MHC基因TSS上游约2kb开始，通过1启动子进入1基因内：这一过程可能增强1基因转录。因此，我们推测，基因间的双向转录控制协调的对立调节相邻的1和2 MHC基因。本研究的目的是通过表观遗传学机制（包括DNA甲基化、染色质重塑和组蛋白修饰）改变心脏MHC基因座上两个相邻基因的表达，研究双向基因间转录的体内调控。为了比较的目的，并作为我们的方法，以了解该基因座的基因调控的一部分，研究也将涉及心房和骨骼肌慢。这些组织的独特之处在于前者主要表达1，而后者仅表达痕量的1，其中2占主导地位。因此，本研究将探索一个新的基因调控领域，并研究一个有趣的调控机制，涉及非编码基因间RNA，通过双向基因间转录的心脏MHC基因位点的表观遗传调控。

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.