Accepted_test

Polytene chromosomes as a tool to identify factors influencing the efficiency of DNA replication initiation
by Kolesnikova T.D. | Vorobyeva N.E. | Cherendina K.P. | Balantaeva M.N. | Dovgan V.V. | Schubert V. | Zhimulev I.F. | Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russia | Institute of Gene Biology RAS, Moscow, Russia | Novosibirsk State University, Novosibirsk, Russia | Novosibirsk State University, Novosibirsk, Russia | Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia | Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, Germany | Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russia
Abstract ID: 55
Event: BGRS-abstracts
Sections: [Sym 11] Section “DNA replication and repair”

In eukaryotic cells, only a small fraction of potential DNA replication initiation sites is used in each cell cycle, and each site is characterized by a certain probability (efficiency) of replication initiation. Drosophila polytene chromosomes provide a unique opportunity to analyze the probabilistic nature of replication initiation at the ultrastructural level. The initiation of replication in polytene chromosomes occurs predominantly in the intervals between the most compact polytene chromosome bands, and within these intervals the initiation is probabilistic.  We identified ~80 very efficient early replication initiation sites, in which initiation occurs on most polytene chromosome strands during the first few minutes of the S phase. Some chromosomal loci demonstrated efficient initiation of replication at all stages of larval development analyzed, whereas others acted as effective replication initiation sites only at certain stages. Many of the sites corresponded to gene loci whose transcription is regulated by the hormone ecdysone. The localization of the identified efficient replication initiation sites on the genomic map and the analysis of the distribution of transcription factors and chromatin modifications led to the conclusion that in salivary gland cells, the most efficient replication origins occur in chromosomal regions containing transcriptional enhancers.

 

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