Topology of nucleosomes in chromatin structure

DNA u eukariotskih kromosoma organizirana je u nukleosome, strukture građene od proteina i DNA, koje predstavljaju osnovnu građevnu i funkcionalnu jedinicu kromosomskog materijala, kromatina. Smatanjem niza nukleosoma nastaje viša razina strukture, kromatinska nit debljine 30 nm. I dok se o strukturi nukleosoma danas praktički sve zna, o 30 nm-niti ali i o višim razinama strukture kromatina još se uvijek malo zna. U ovom radu izloženi su modeli koji pokušavaju objasniti strukturu kromatinske niti: solenoidni model, model zavijene vrpce, dvopočetni ukriženi model te nesekvencijski jednopočetni model, sa razlikom u putu koji prelazi DNA između dva nukleosoma. Razumijevanje strukture 30 nm-niti od izuzetne je važnosti za shvaćanje regulacije procesa transkripcije, rekombinacije, DNA popravka te replikacije.DNA in eukaryotic chromosomes is organized in the nucleosomes, structures which contain proteins and DNA, and which represent elementary structural and functional unit of chromosomal material, chromatin. Arrays of nucleosomes are folded into higher order structure, 30 nm chromatin fiber. Although the structure of nucleosome is known in smallest detail, only a few facts are known about 30 nm fibre and higher chromatin structures. In this work, I exposed models for structure of 30 nm chromatin fibers: solenoid, twisted-ribbon, two-started crossed-linker and one-started nonsequential model, with difference in the path of DNA between two nucleosomes. Uncovering of 30 nm fibre structure is crucial for understanding the regulation of processes such as transcription, recombination, DNA repair and replication