Effects of Mutations in the Drosophila melanogaster Rif1 Gene on the Replication and Underreplication of Pericentromeric Heterochromatin in Salivary Gland Polytene Chromosomes
Open Access
- 19 June 2020
- Vol. 9 (6), 1501
- https://doi.org/10.3390/cells9061501
Abstract
In Drosophila salivary gland polytene chromosomes, a substantial portion of heterochromatin is underreplicated. The combination of mutations SuURES and Su(var)3-906 results in the polytenization of a substantial fraction of unique and moderately repeated sequences but has almost no effect on satellite DNA replication. The Rap1 interacting factor 1 (Rif) protein is a conserved regulator of replication timing, and in Drosophila, it affects underreplication in polytene chromosomes. We compared the morphology of pericentromeric regions and labeling patterns of in situ hybridization of heterochromatin-specific DNA probes between wild-type salivary gland polytene chromosomes and the chromosomes of Rif1 mutants and SuUR Su(var)3-906 double mutants. We show that, despite general similarities, heterochromatin zones exist that are polytenized only in the Rif1 mutants, and that there are zones that are under specific control of Su(var)3-9. In the Rif1 mutants, we found additional polytenization of the largest blocks of satellite DNA (in particular, satellite 1.688 of chromosome X and simple satellites in chromosomes X and 4) as well as partial polytenization of chromosome Y. Data on pulsed incorporation of 5-ethynyl-2′-deoxyuridine (EdU) into polytene chromosomes indicated that in the Rif1 mutants, just as in the wild type, most of the heterochromatin becomes replicated during the late S phase. Nevertheless, a significantly increased number of heterochromatin replicons was noted. These results suggest that Rif1 regulates the activation probability of heterochromatic origins in the satellite DNA region.Keywords
Funding Information
- Russian Science Foundation (19-14-00051)
- Russian Foundation for Basic Research (20-54-12016)
- Deutsche Forschungsgemeinschaft (Schu762/12-1)
This publication has 115 references indexed in Scilit:
- Mapping the pericentric heterochromatin by comparative genomic hybridization analysis and chromosome deletions in Drosophila melanogasterGenome Research, 2012
- Regulation of DNA replication during developmentDevelopment, 2012
- Rif1 is a global regulator of timing of replication origin firing in fission yeastGenes & Development, 2012
- Developmental control of gene copy number by repression of replication initiation and fork progressionGenome Research, 2011
- Dampened activity of E2F1–DP and Myb–MuvB transcription factors inDrosophilaendocycling cellsJournal of Cell Science, 2010
- Endoreplication: polyploidy with purposeGenes & Development, 2009
- Endocycling cells do not apoptose in response to DNA rereplication genotoxic stressGenes & Development, 2008
- High-resolution analysis of Drosophila heterochromatin organization using SuUR Su(var)3-9 double mutantsProceedings of the National Academy of Sciences of the United States of America, 2007
- Sequence Finishing and Mapping of Drosophila melanogaster HeterochromatinScience, 2007
- New insights into cell cycle control from the Drosophila endocycleOncogene, 2005