TY - JOUR

T1 - Effects of Mutations in the Drosophila melanogaster Rif1 Gene on the Replication and Underreplication of Pericentromeric Heterochromatin in Salivary Gland Polytene Chromosomes

AU - Kolesnikova, Tatyana D.

AU - Kolodyazhnaya, Alexandra V.

AU - Pokholkova, Galina V.

AU - Schubert, Veit

AU - Dovgan, Viktoria V.

AU - Romanenko, Svetlana A.

AU - Prokopov, Dmitry Yu

AU - Zhimulev, Igor F.

PY - 2020/6/19

Y1 - 2020/6/19

N2 - 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.

AB - 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.

KW - Drosophila melanogaster

KW - heterochromatin

KW - polytene chromosomes

KW - replication timing

KW - Rif1

KW - satellite DNA

KW - Su(var)3-9

KW - SuUR

KW - underreplication

KW - X-CHROMOSOME

KW - BETA-HETEROCHROMATIN

KW - DROSOPHILA-MELANOGASTER

KW - MUTANT SUPPRESSOR

KW - ACTIVE ORIGINS

KW - CYTOGENETIC ANALYSIS

KW - PHASE-SEPARATION

KW - SATELLITE DNA-SEQUENCES

KW - PROTEIN PHOSPHATASE 1

KW - S-PHASE

UR - http://www.scopus.com/inward/record.url?scp=85087025302&partnerID=8YFLogxK

U2 - 10.3390/cells9061501

DO - 10.3390/cells9061501

M3 - Article

C2 - 32575592

AN - SCOPUS:85087025302

VL - 9

JO - Cells

JF - Cells

SN - 2073-4409

IS - 6

M1 - 1501

ER -