Chromosomal surfaces are ornamented with a variety of posttranslational modifications of histones, which are required for the regulation of many of the DNA-templated processes. Such histone modifications include acetylation, sumoylation, phosphorylation, ubiquitination and methylation. Histone modifications can either function by disrupting chromosomal contacts or by regulating nonhistone protein interactions with chromatin. In this review, recent findings will be discussed regarding the regulation of the implementation and physiological significance for one such histone modification, histone H3 Lysine 4 (H3K4) methylation by the yeast COMPASS and mammalian COMPASS-like complexes.All DNA-templated processes are regulated by chromatin and its posttranslational modifications. The nucleosome, which is the fundamental unit of chromatin, is composed of 146 base pairs of DNA wrapped twice around an octamer of the four core histones (H3, H4, H2A, and H2B) [1][2][3]. Structural studies demonstrated that the unstructured histone N-terminal tails protrude outward from the nucleosomes and are available for interactions with other neighboring histones or non-histone proteins. Many residues within the histone N-terminal tails and a few within the histone core can be altered by posttranslational modifications [1]. To date, there are at least five types of posttranslational modifications found on histones, these include: acetylation, phosphorylation, ubiquitination, sumoylation, and methylation [4,5]. Almost all of these modifications have been shown to be reversible, and their implementation and removal are fundamental to the regulation of a diverse set of biological processes such as replication, repair, recombination, transcription and RNA processing [4,5]. This review will focus mainly on the most recent studies of one type of histone modification, histone H3 lysine 4 (H3K4) methylation.
Histone lysine methylationHistones are methylated either on their arginine and/or lysine residues [6,7]. The lysine residues are methylated on the ε-nitrogen by either the SET domain or the non-SET domain-containing lysine methyltransferases (KMTs). A large number of enzymes have been characterized which are capable of methylating specific lysine residues on histones ( Table 1). The ε-nitrogen can also be modified by lysine acetyl transferases (KATs) and methylation and acetylation of lysine are mutually exclusive. Indeed, many sites of histone methylation are also sites of acetylation.Correspondence and proofs should be sent to the following address: Ali Shilatifard, Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, Office (816) 926-4465, Email: ASH@Stowers-Institute.org. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable for...