The Assembly And Maintenance Of Heterochromatin

1295 words - 5 pages

Heterochromatin upholds several critical functions which are important for the cell. Heterochromatin can either be constitutive or facultative both of which plays a major role in expression of genes. Importance of heterochromatin reflects as to why plants use several pathways to maintain it. Here we will discuss some of these pathways.

INTRODUCTION

Two states of chromatin are known as euchromatin and heterochromatin. Tightly packed form of DNA is called heterochromatin which is enriched at the centromeres and telomeres of chromosomes. The dense packing of DNA makes it less accessible to several protein factors and hence is often described as the gene-poor part of the genome. Heterochromatin is primarily composed of highly repetitive sequences such as satellite sequences, ribosomal DNA (rDNA) and transposable elements (1). It localizes at the nuclear periphery and nucleolus. Its formation involves recruitment of histone-binding factors. Propagation of heterochomatic status involves several epigenetic modifications such as DNA methylation, histone variants, non-coding RNA and histone modifications, methylation of histone H3 at lysine 9 being the distinct one.

Non-CpG Methylation

Besides CpG methylation, plants also have non-CpG methylation throughout its development. DNA methylation occurs at three different contexts namely, CG, CHG and CHH, where H is either A, C or T. Different proteins play roles in different contexts. DNA methylation depends on METHYLTRASFERASE1 (MET1) for CG, CHROMOMETHYLASE3 (CMT3) for CHG and DOMAIN REARRANGED METHYLTRANSFERASE2 (DRM2) for CHH (2, 3, 4). Dimethylation of H3K9 (H3K9me2) is mainly associated with the heterochromatic transposable elements (TEs) (5). CHG-containing oligonucleotides are directly bound by the SRA domain of the H3K9 methyltransferase KRYPTONITE (KYP) (6). A self-reinforcing loop was suggested, in which methylated CHG DNA recruits KYP to maintain methylation of H3K9 whereas H3K9me2 recruits CMT3 to methylate CHG (3, 6). During several rounds of replication if methylation is not properly maintained then the fully methylated DNA can become hemimethylated and eventually unmethylated DNA. In order to prevent this CMT3 acts as a maintenance methyltransferase by efficiently converting hemimethylated DNA to fully methylated DNA. One plausible model suggested to imply that methylation of CMT3 takes place during DNA replication is that either CMT3 is displaced from nucleosome during replication and is recruited back to the methylated newly assembled nucleosomes after the completion of replication or CMT3 may be recruited to the chromatin by pre-modified H3K9me2 marks from parental histones during DNA replication (7). A dual-recognition mechanism ensures a higher fidelity of CHG DNA methylation, in which the CMT3 bromo adjacent homology (BAH) and chromo domains simultaneously read the H3K9me2 on the two tails emanating from a single nucleosome.

Histone codes, marks and variants

Core histones H2A,...

Find Another Essay On The Assembly and Maintenance of Heterochromatin

Maintenance of the JSTARS Essay

1208 words - 5 pages The Joint Surveillance and Target Attack Radar System (JSTARS) is a project of the US Air Force and the Department of the Army. JSTARS serves as a theater Battle Management and Command and Control Intelligence, Surveillance, and Reconnaissance (C2ISR) platform that provides support to joint, interagency and multinational commanders and components (“Northrop Grumman,” n.d.). JSTARS includes airborne and ground-based components and connectivity

Zen and the Art of Motorcycle Maintenance and Quality

926 words - 4 pages Zen and the Art of Motorcycle Maintenance And Quality Zen and the Art of Motorcycle Maintenance as written by Robert Pirsig, focuses on a number of philosophical life values. These values include quality, identity, duality, and Zen. This paper will focus mainly on the subject of quality and the effect dwelling on its definition had on Pirsig. Pirsig has put an incredible amount of thought into defining Quality. Starting just about at the

Robert Pirsig's Zen and the Art of Motorcycle Maintenance

5301 words - 21 pages Robert Pirsig's Zen and the Art of Motorcycle Maintenance: An Inquiry into Values Confronting crises of technological annihilation and personal madness, Robert Pirsig finds each to be a manifestation of a deeper crisis of Reason. In response) he suggests an alternative to our current paradigm of rationality, the "art of motorcycle maintenance." By showing that our understanding and performance derive from our emotional and evaluative

Creation and Maintenance of the Business Culture at Lincoln Electric

998 words - 4 pages operational values to every new employee. The maintenance process of transferring the cultural values at Lincoln Electric will now be analyzed by examining four distinct processes proposed by Carpenter et al. (2009): i. Attraction-Selection-Attrition (referred to as ASA) is one process through which the culture at Lincoln Electric was maintained. Jobs at Lincoln are premium and every vacant position is advertised internally first. Promotions are

Ethnic Identity and the Maintenance of Heritage Languages

4082 words - 16 pages Ethnic Identity and the Maintenance of Heritage Languages ‘Neither ethnicity nor mother tongue nor even identities can be treated as things, commodities, that one can choose and discard like an old coat at will’ ~Tove Skutnabb-Kangas (qtd in Fishman 55) Broadly speaking, “language policy” in the United States is thought of as a covert policy. Schiffman (2000) writes of the challenges of researching this field, given that

Speaker of the House or Assembly

697 words - 3 pages The Speaker of the House is J. Dennis Hastert (R-IL).Speaker of the House or Assembly. The speaker is the principal leader of the House or Assembly. The speaker typically will (1) preside over the daily sessions of the Senate, (2) preserve order in the chamber, (3) state parliamentary motions, (4) rule on parliamentary questions, (4) appoint committee chairs and members, (5) refer bills to committee, (6) sign legislation, writs and warrants and

Testing and Maintenance of Disaster Recovery Plans

2307 words - 9 pages with portions of senior and mid-level management positions. Oklahoma, maintains senior and mid-level management level positions that work in combination with the leadership and operations in Florida. In this article, we will discuss employee involvement in the testing and maintenance of the organizations BC/DR plan and the testing of the plan. Furthermore, a brief explanation on the importance of plan evaluation will be examined. Organizational

Management and Maintenance of Commercial Piggeries

1001 words - 5 pages Commercial piggeries face the challenge to effectively utilise housing management options to optimise productivity while maintaining animal welfare. The common use of farrowing crates is often a subject of contention as crates are spatially restricting and thought to inhibit natural behaviours (Hales et al., 2014). Increased public awareness of this animal welfare issue has pressured producers to adopt the use of pens as an alternative. The use

Winter Maintenance and the Advocacy Process

1498 words - 6 pages resolution of an issue is dependent on how adequate the following measures are established; a clear identification of an issue, collection of relevant data, involvement of interested people, development and maintenance of alliances and coalitions, publicising the issue of concern for further involvement of the public, and the concluding step for resolution is to contact the individual, or group of interest with influential factors over the issue

THE IMPORTANCE OF PROPER AIRCRAFT MAINTENANCE

1196 words - 5 pages As the development of aviation industry grows, more and more aircraft crashes occur. There are many reasons that lead to aircraft crashes, but one of them, is because of improper aircraft maintenance. Why is proper aircraft maintenance so important? Proper aircraft maintenance is critical in order to keep the aircraft can function properly, every aircraft part is in good condition and ensure the safety of pilots and passengers. Proper

The Growth of the Automobile Industry: The Assembly Line

822 words - 4 pages The growth of the automobile industry caused an economic revolution across the United States. The beginning of the 20th century, horse-drawn vehicles and the railroads were the dominant sources for transportation of both goods and people. Before the assembly line each vehicle was created individually. The assembly line created by Henry Ford, made automobile production faster and easier. The assembly line doubled production and reduced costs

Similar Essays

History And Benefits Of The Assembly Line

3659 words - 15 pages that are contributing to this problem can be due to improper scheduling, improper line balancing and machine breakdown or equipment maintenance (Hapaz, 2008). 1.2 Problem Statement The product in flow assembly line moves from one station to another workstation. Unbalance workloads in the workstations causing the product to get stuck due to accumulation in certain workstation, as it exceeds the cycle time in that station. Movement of product between

Zen And The Art Of Motorcycle Maintenance

1759 words - 7 pages Told by the blurb that we have here "one of the most unique and exciting books in the history of American letters," one bridles both at the grammar of the claim and at its routine excess. The grammar stays irreparable. But I have a hunch that the assertion itself is valid. Zen and the Art of Motorcycle Maintenance: An Inquiry Into Values, by Robert M. Pirsig (Morrow), is as willfully awkward as its title. It is densely put together. It lurches

The Assembly And Components Of The Boeing 727

706 words - 3 pages Objectives: There are thousands of jobs performed on the Queen of the sky, the Boeing 747 also called as the jumbo jet, for its final assembly. 747 is an advanced long range airliner, it is a product of complex, demanding collaborative design process. 747 is an icon of the modern age. It is the longest airliner in the world. This system is comprised of components which are complex, independent and interacts to achieve a common goal

The Assembly Of First Nations Essay

1639 words - 7 pages Throughout the history of Canada the indigenous population of the country have been voiceless. They have been both suppressed and oppressed by the Federal and various Provincial governments within Canada. Many organizations tried to provide a voice for the native population but failed in their attempt. These organizations eventually merged together to become what is now known as The Assembly of First Nations. The Assembly of First Nations gives