Малые интерферирующие РНК: различия между версиями

== Активация РНК ==
Двуцепочечные РНК могут активировать экспрессию генов по механизму, называемому активацией генов малыми РНК ({{lang-en|RNAa, small RNA-induced gene activation}}). Показано, что двуцепочечные РНК, комплементарные промоторам генов-мишеней вызывают активацию соответствующих генов. Активация РНК при введении синтетических двуцепочечных РНК (малых активирующих РНК, {{lang-en|small activating RNA}}) в клетки человека. Не известно, имеется ли подобная система в клетках других организмов.<ref name= LiLC>{{cite book |chapterurl=http://www.horizonpress.com/rnareg|author= Li LC|year=2008|chapter=Small RNA-Mediated Gene Activation|title=RNA and the Regulation of Gene Expression: A Hidden Layer of Complexity|publisher=Caister Academic Press|id=[http://www.horizonpress.com/rnareg ISBN 978-1-904455-25-7]}}</ref>
== Трудности: исключение неспецифических эффектов ==
Поскольку [[РНК-интерференция]] пересекается со множеством других цепочек реакций, не удивительно, что прии экспериментальном введении миРНК могут включаться неспецифические эффекты. Когда клетка млекопитающих встречает двукцепочечную РНК, такую как мнРНК, она может принять ее за продукт вируса и запустить иммунный ответ. Кроме того, because, поскольку структурно связанные [[микроРНК]] модулируют экспрессию генов главным образом через взаимодействие c матричной РНК (мРНК), которая служит им целью, посредством неполностью комплементарных пар осенований, введение миРНК может вызвать нежелательный эффект потери цели.
=== Врожденный иммунитет ===
Введение слишком большого количества миРНК может вызвать побочные эффекты из-за того, что включается врожденный иммунный ответ. Большая часть данных на сегодняшний день говорит о том, что это вероятно происходит из-за активации протеин-киназы R, которая чувствительна к миРНК, хотя ген RIG I (retinoic acid inducible gene I) тоже может участвовать. Описаны также случаи индукции цитокинов рецептор TLR 7 (toll-like receptor 7).
One promising method of reducing the nonspecific effects is to convert the siRNA into a microRNA. MicroRNAs occur naturally, and by harnessing this endogenous pathway it should be possible to achieve similar gene knockdown at comparatively low concentrations of resulting siRNAs. This should minimize nonspecific effects.
=== Побочные эффекты ===
Off-targeting is another challenge to the use of siRNAs as a gene knockdown tool. Here, genes with incomplete complementarity are inadvertently downregulated by the siRNA (effectively, the siRNA acts as a miRNA), leading to problems in data interpretation and potential toxicity. This, however, can be partly addressed by designing appropriate control experiments, and siRNA design algorithms are currently being developed to produce siRNAs free from off-targeting. Genome-wide expression analysis, e.g., by microarray technology, can then be used to verify this and further refine the algorithms. A 2006 paper from the laboratory of Dr. Khvorova implicates 6- or 7-basepair-long stretches from position 2 onward in the siRNA matching with 3’UTR regions in off-targeted genes.<ref>{{cite journal |author=Birmingham A, Anderson E, Reynolds A, Ilsley-Tyree D, Leake D, Fedorov Y, Baskerville S, Maksimova E, Robinson K, Karpilow J, Marshall W, Khvorova A |title=3' UTR seed matches, but not overall identity, are associated with RNAi off-targets |journal=Nat Methods |volume=3 |issue=3 |pages=199–204 |year=2006 |doi= 10.1038/nmeth854 |pmid=16489337}}</ref>
== Перспективы применения в терапии ==
Given the ability to knock down essentially any gene of interest, RNAi via siRNAs has generated a great deal of interest in both basic<ref>Alekseev OM, Richardson RT, Alekseev O, O’Rand MG. Analysis of gene expression profiles in HeLa cells in response to overexpression or siRNA-mediated depletion of NASP. Reprod Biol Endocrinol. 2009 May 13;7:45.PMID: 19439102</ref> and applied biology. There are an increasing number of large-scale RNAi screens that are designed to identify the important genes in various biological pathways. Because disease processes also depend on the activity of multiple genes, it is expected that in some situations turning off the activity of a gene with an siRNA could produce a therapeutic benefit.
However, applying RNAi via siRNAs to living animals, especially humans, poses many challenges. Experimentally, siRNAs show different effectiveness in different cell types in a manner as yet poorly understood: some cells respond well to siRNAs and show a robust knockdown, whereas others show no such knockdown (even despite efficient [[transfection]]).
Phase I results of the first two therapeutic RNAi trials (indicated for [[age-related macular degeneration]], aka AMD) reported at the end of 2005 demonstrated that siRNAs are well tolerated and have suitable pharmacokinetic properties.<ref>{{cite news | url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/08/11/BUGPNKFU6T1.DTL | publisher=San Francisco Chronicle | author=Tansey B | title=Macular degeneration treatment interferes with RNA messages | date=11 August 2006}}</ref> siRNAs and related RNAi induction methods therefore stand to become an important new class of drugs in the foreseeable future.
In 2008, a team of researchers from [[Texas Tech University]] and [[Harvard University]] announced the development of a siRNA-based treatment that may ultimately counteract the [[HIV|Human Immunodeficiency Virus (HIV)]]. Human cells infected with HIV, injected into rats, have been cured by the experimental treatment. Clinical trials on humans are expected to begin by 2010.<ref>{{cite news|title=Texas Tech Researchers May Have Found AIDS Cure|publisher=[[KCBD]]|date=2008-08-07|url=http://www.kcbd.com/Global/story.asp?S=8808748|accessdate=2008-08-16}}</ref><ref>{{cite news|last=Swaminathan|first=Nikhil|title=Researchers Silence HIV in Mice Engineered to Be Like Humans|work=[[Scientific American]]|date=2008-08-07|url=http://www.sciam.com/article.cfm?id=researchers-silence-hiv-in-human-like-mice-rnai|accessdate=2008-08-16}}</ref><ref>{{cite web|title=Researchers halt spread of HIV with RNAi|publisher=[[Harvard Medical School]]|url=
In 2008 a novel DNA-siRNA delivery system that could lead to more efficient and more disease-specific vaccines against infectious diseases was developed by researchers at The [[University of Texas at Austin]]. Biomaterials based micron size particles carrying both the DNA vaccine and the siRNA to immune cells show potential to divert immune response in desirable directions <ref>[http://www.bme.utexas.edu/news/2008_roy_VDS.cfm. RNA molecules, delivery system improve vaccine responses, effectiveness<!-- Заголовок добавлен ботом -->]</ref>
== Примечания ==