The role of kinesin-8 and PRC1 proteins in kinetochorepositioning in the metaphase plate

doctoral thesis

• Title (croatian): Uloga proteina kinezina-8 i PRC1 u smještanju kinetohora u metafaznoj ravnini
• Author: Mihaela Jagrić
• Mentor: Iva Marija Tolić (mentor)
• Committee member: Juraj Simunić (predsjednik povjerenstva)
• Committee member: Inga Urlić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2021-02-09, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology
• Universal decimal classification (UDC): 577 - Biochemistry. Molecular biology. Biophysics

Abstract

U metafazi mitoze kromosomi se poravnavaju u ekvatorijalnoj ravnini diobenog vretena što je
od ključne važnosti za pravilan završetak kasnijih faza. Poravnavanje kromosoma regulirano
je silama dinamike kinetohornih vlakana (k-vlakana) te silama odbijanja na polovima. U
ovome radu istražena je uloga kinezina-8 u poravnavanju kromosoma, koji je jedan od
glavnih regulatora dinamike k-vlakana. Pokazala sam kako kinezin-8 regulira brzinu i
amplitudu kretanja kinetohora, dok eksperimenti laserskog rezanja k-vlakana nakon deplecije
kinezina-8 upućuju na njegovu ulogu u ograničavanju rasta mikrotubula.
Nadalje, ulogu u poravnavanju kromosoma mogla bi imati premošćujuća vlakna, nova klasa
mikrotubula u vretenu koja povezuje sestrinska k-vlakna i balansira silu tenzije na sestrinskim
kinetohorama. Ova mogućnost istražena je razvitkom i primjenom optogenetičkog pristupa za
manipulaciju lokalizacije proteina PRC1 koji specifično povezuje mikrotubule u
premošćujućim vlaknima. Akutno uklanjanje proteina PRC1 dovelo je do djelomičnog
raspada premošćujućih vlakana i produljenja njihovih antiparalelnih preklopa, uz pojavu
neporavnatih i zaostajućih kromosoma. Kif4A/kinezin-4 i Kif18A/kinezin-8 uočeni su u
premošćujućim vlaknima, no većinom izgubljeni nakon uklanjanja PRC1, što upućuje na to
da ovi proteini reguliraju duljine preklopa premošćujućih mikrotubula. Zaključno, predložen
je model prema kojemu PRC1 povezujući mikrotubule u premošćujućim vlaknima i
regrutiranjem kinezina u premošćujuća vlakna pospješuje poravnanje kromosoma silama
ovisnim o duljini preklopa koje se posredno prenose na k-vlakna.

Abstract (english)

In metaphase of mitosis, chromosomes align at the equatorial plane of the spindle, which is
crucial for correct completion of later phases. Chromosome alignment is regulated by forces
exerted by dynamics of kinetochore fibers (k-fibers) and polar ejection forces. This study
explored a role of motor protein kinesin-8, which is known as one of main regulators of kfiber
dynamics, in chromosome alignment. Here, I showed that kinesin-8 regulates velocity
and amplitude of kinetochore movements, while experiments of laser ablation of k-fibers after
depletion of kinesin-8 indicate it has a role in limiting the growth of microtubules.
Furthermore, chromosome alignment could be influenced by bridging fibers, new class of
microtubules in the spindle that connect sister k-fibers and balance the tension on sister
kinetochores. This possibility is investigated by developing and applying optogenetic
approach to manipulate localization of PRC1 protein, which specifically crosslinks
microtubules within the bridging fibers. Acute removal of PRC1 led to partial disassembly of
bridging fibers and elongation of their antiparallel overlaps, which was accompanied by
misaligned and lagging chromosomes. Kif4A/kinesin-4 and Kif18A/kinesin-8 were also
found within bridging fibers and largely lost upon PRC1 removal, suggesting that these
proteins regulate the overlap length of bridging microtubules. Finally, a model is proposed
where PRC1-mediated crosslinking of bridging microtubules and recruitment of kinesins to
the bridging fiber promote chromosome alignment by overlap length-dependent forces
transmitted to the associated k-fibers.

• Keywords: kinezin-8; PRC1; premošćujuća vlakna; optogenetika; poravnanje kromosom
• Keywords (english): kinesin-8; PRC1; bridging fibers; optogenetics; chromosome alignment
• Language: english
• URN:NBN: urn:nbn:hr:217:286908
• Promotion: 2021
• Study programme: Title: Biology; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje biologija (doktor/doktorica znanosti, područje prirodnih znanosti, polje biologija)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-03-09 10:02:31