Struktura i dinamika kompleksa za prekrajanje RNA

undergraduate thesis

• Title (english): The structure and dynamics of the spliceosome
• Author: Anamaria Elek
• Mentor: Jasmina Rokov Plavec (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2016, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Eukariotski geni između kodirajućih sljedova, eksona, sadrže dugačke nekodirajuće introne. Geni se u cijelosti prepisuju u primarne transkripte mRNA, a introni se naknadno izrezuju djelovanjem multi-megadaltonskog ribonukleoproteinskog kompleksa za prekrajanje (eng. spliceosome). Ovaj kompleks sastavlja se postepeno u jezgri eukariotske stanice, na odgovarajućem pre-mRNA supstratu, a potom se aktivira kako bi mogao katalizirati reakcije izrezivanja introna i povezivanja eksona u zrelu molekulu mRNA. Najznačajnije karakteristike ovog kompleksa njegova su veličina (preko 3 MDa), brojnost komponenti (preko 200 proteina i 5 molekula RNA) te ribozimska i metaloenzimska priroda. Evolucijski očuvani elementi sekundarne strukture molekula RNA u aktivnom mjestu kompleksa imaju ključne katalitičke uloge, poput koordinacije metalnih iona, dok su proteini u ciklusu prekrajanja prvenstveno odgovorni za ispravno pozicioniranje i stabilizaciju ovih struktura. Još jedna značajna karakteristika je i izuzetna plastičnost kompleksa koja je dijelom posljedica velikog broja strukturno neuređenih proteina, a koja omogućuje uspješno prepoznavanje i izrezivanje introna iz najrazličitijih transkripata pre-mRNA. Izrezivanje introna mora biti izuzetno precizno ali i brzo, kako bi se u citoplazmu iz jezgre iznosile samo ispravno dorađene mRNA molekule. Stoga su stavljanje kompleksa, aktivacija i kataliza regulirani posttranslacijkskim modifikacijama i djelovanjem enzima koji uz utrošak ATP-a osiguravaju točnost ovih reakcija, a sve ključne reakcije ciklusa su reverzibilne. Prekrajanje je usto djelomično koordinirano s transkripcijom i drugim reakcijama metabolizma RNA. Nakon dovršetka reakcija prekrajanja, kompleks se rastavlja. Produkti reakcija, zrela mRNA i intron u obliku omče, jedan za drugim disociraju, kao u konačnici i komponente kompleksa koje se onda mogu uključiti u novi ciklus na drugom pre-mRNA supstratu.

Abstract (english)

Nuclear pre-mRNA splicing is catalysed by the spliceosome, multi-megadalton ribonucleoprotein complex which is assembled in stepwise fashion and activated while bound to its substrate. Defining features of this complex are its size (over 3 MDa), myriad of components (more than 200 proteins and 5 RNAs), and the fact that it is a ribozyme, as well as a metaloenzyme. Evolutionary conserved elements in the secondary structure of RNAs carry out important catalytic functions, such as coordination of catalytic metal ions in the active site, while protein components are found to assist in formation of these secondary structures, as well as in stabilising their interactions. Another important characteristic of the spliceosome is its remarkable plasticity, which is in part due to a large number of intrinsically disordered proteins. This allows for introns from a wide range of vastly different pre-mRNA substrates to be successfully spliced. Splicing must be fast and precise at once, so as to assure that only the correctly spliced and modified RNAs are exported from nucleus to cytoplasm. To achieve this, spliceosome assembly, activation, and catalysis are highly regulated by different posttranslational modifications and through the action of the several enzymes that utilize ATP in order to maintain splicing reaction fidelity. In addition, all of the main reactions in the spliceosome cycle are reversible. Splicing is also, at least to some extent, coordinated with transcription and RNA metabolism which take place in the nucleus. Following the completion of splicing reactions, mature mRNA and intron in the form of lariat sequentially dissociate, as do the components of the spliceosome. These are then recycled in another spliceosome cycle.

• Keywords: prekrajanje RNA
• Keywords (english): spliceosome
• Language: croatian
• URN:NBN: urn:nbn:hr:217:116799
• Study programme: Title: Molecular Biology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-01-02 09:27:59