OPOMNIK: IJS KOLOKVIJ, sreda, 03. 04. 2013; ob 13. uri; prof. dr. Cristian Micheletti

[Barbara Hrovatin]

Vabimo vas na 15. predavanje iz sklopa "Kolokviji na IJS" v letu 2012/13, ki
bo v sredo, 3. aprila 2013, ob 13. uri v Veliki predavalnici Instituta
>Jožef Stefan< na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete
tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke
preteklih predavanj pa na http://videolectures.net/kolokviji_ijs.

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prof. dr. Cristian Micheletti

International school for Advanced Studies (SISSA), Trst, Italija

 

Prepletene niti življenja

 

Vozli so del vsakdanjega življenja. V nekaterih primerih so koristni, npr.
pri plezanju ali jadranju. V drugih so nadloga, kot nas učijo izkušnje pri
razvozlavanju električnih kablov ali telefonskih žic. Dolgi in tesno zloženi
biopolimeri, kakršna je DNA, so lahko zavozlani podobno kot električni
kabli. V vrsti bioloških sistemov škodljivi učinek vozlanja DNA (ki med
drugim zavira transkripcijo in replikacijo) omejujejo encimi, ki DNA režejo,
razvozlavanjo in nanovo zlepijo. V zelo majhnih virusih, v katerih je
prostora le za samo DNA, se vozli neogibno nabirajo zaradi tesne ograditve.
Ti vozli, ki jih lahko eksperimentalno zaznamo, pa vseeno ne zavrejo
translokacije DNA iz virusa v inficirano celico. Da bi dobili vpogled v te
pomembne procese, smo analizirali važne, a posredne dokaze pakiranja DNA, ki
jih nudijo eksperimentalne študije vozlanja DNA. Začenši s pogostnostjo
določenih vrst vozlov (posebej toroidnih vozlov) smo pokazali, da igra pri
tem težnja sosednih DNA niti po vzporedni orientaciji zelo pomembno vlogo
pri prostorski organizaciji in vozlanju spakirane DNA. Z eksplicitnim
modeliranjem te interakcije, ki je analogna tisti v kiralnih nematskih
materialih, smo nadalje raziskovali iztiskanje DNA iz kapside in ugotovili,
da ni povezano s stopnjo zavozlanosti.

Predavanje bo v angleščini.

Lepo vabljeni!

 

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We invite you to the 15th Institute colloquium in the academic year 2012/13.
The colloquium will be held on Wednesday April 3, 2013 at 1 PM in the main
Institute lecture hall, Jamova 39, Ljubljana. To read the abstract click
http://www.ijs.si/ijsw/Koledar_prireditev. Past colloquia are posted on
http://videolectures.net/kolokviji_ijs.

 

********************************************

prof. dr. Cristian Micheletti

International school for Advanced Studies (SISSA), Trieste, Italy

 

The knotted strands of life

 

Knots are part of our everyday life. In some cases they can serve useful
purposes, think for instance of climbing or sailing. In other cases they can
be a nuisance, as we know from the laborious procedures of disentangling
extension cables or headphone wires. Like extension cables, long and densely
packed biopolymers such as DNA can be knotted too. In several biological
systems the detrimental effects of DNA knotting (which e.g. hinders the
transcription and replication)  are kept at bay by enzymes that cut,
disentangle and reseal DNA strands. However, within very small viruses,
where there is space only for the DNA itself, knots inevitably accumulate
because of the tight confinement. Yet these knots, which can be
experimentally detected, do not prevent the translocation of the DNA from
the virus to the infected cell.

To gain insight into these important processes, we analysed the powerful,
albeit indirect clues on viral DNA packaging offered by experiments on viral
DNA knotting. In particular, starting from the abundance of certain knot
types (torus knots) we established that the aligning tendency of contacting
DNA strands plays a major role in guiding the spatial organization and
knotting of the packaged DNA. By explicitly modelling this aligning
interaction, which is analogous to the one observed in cholesteric
materials, we further investigated the DNA ejection process and observed
that it is not affected by the degree of knotting.

 

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