TY - JOUR

T1 - A Spontaneous Inversion of the X Chromosome Heterochromatin Provides a Tool for Studying the Structure and Activity of the Nucleolus in Drosophila melanogaster

AU - Kolesnikova, Tatyana D.

AU - Klenov, Mikhail S.

AU - Nokhova, Alina R.

AU - Lavrov, Sergey A.

AU - Pokholkova, Galina V.

AU - Schubert, Veit

AU - Maltseva, Svetlana V.

AU - Cook, Kevin R.

AU - Dixon, Michael J.

AU - Zhimulev, Igor F.

N1 - Funding Information: The part of the work associated with nanopore sequencing was funded by the Russian Science Foundation (RSF) (grant number 19-74-20178). Part of the work related to the visualization of nucleolar components was supported by a grant from the Russian Science Foundation (19-14-00382). The part of the work associated with ultrastructural polytene chromosome analysis was funded by a joint Russian-German grant from the Russian Foundation for Basic Research (No. 20-54-12016) and the Deutsche Forschungsgemeinschaft (Schu762/12-1). The part of the work associated with the new inversion cytological mapping was funded by the Russian Science Foundation grant No. 19-14-00051. Work at the Bloomington Drosophila Stock Center was supported by the U.S. National Institutes of Health grant P40 OD018537. Publisher Copyright: © 2022 by the authors.

PY - 2022/12

Y1 - 2022/12

N2 - The pericentromeric heterochromatin is largely composed of repetitive sequences, making it difficult to analyze with standard molecular biological methods. At the same time, it carries many functional elements with poorly understood mechanisms of action. The search for new experimental models for the analysis of heterochromatin is an urgent task. In this work, we used the Rif1 mutation, which suppresses the underreplication of all types of repeated sequences, to analyze heterochromatin regions in polytene chromosomes of Drosophila melanogaster. In the Rif1 background, we discovered and described in detail a new inversion, In(1)19EHet, which arose on a chromosome already carrying the In(1)sc8 inversion and transferred a large part of X chromosome heterochromatin, including the nucleolar organizer to a new euchromatic environment. Using nanopore sequencing and FISH, we have identified the eu- and heterochromatin breakpoints of In(1)19EHet. The combination of the new inversion and the Rif1 mutation provides a promising tool for studies of X chromosome heterochromatin structure, nucleolar organization, and the nucleolar dominance phenomenon. In particular, we found that, with the complete polytenization of rDNA repeats, the nucleolus consists of a cloud-like structure corresponding to the classical nucleolus of polytene chromosomes, as well as an unusual intrachromosomal structure containing alternating transcriptionally active and inactive regions.

AB - The pericentromeric heterochromatin is largely composed of repetitive sequences, making it difficult to analyze with standard molecular biological methods. At the same time, it carries many functional elements with poorly understood mechanisms of action. The search for new experimental models for the analysis of heterochromatin is an urgent task. In this work, we used the Rif1 mutation, which suppresses the underreplication of all types of repeated sequences, to analyze heterochromatin regions in polytene chromosomes of Drosophila melanogaster. In the Rif1 background, we discovered and described in detail a new inversion, In(1)19EHet, which arose on a chromosome already carrying the In(1)sc8 inversion and transferred a large part of X chromosome heterochromatin, including the nucleolar organizer to a new euchromatic environment. Using nanopore sequencing and FISH, we have identified the eu- and heterochromatin breakpoints of In(1)19EHet. The combination of the new inversion and the Rif1 mutation provides a promising tool for studies of X chromosome heterochromatin structure, nucleolar organization, and the nucleolar dominance phenomenon. In particular, we found that, with the complete polytenization of rDNA repeats, the nucleolus consists of a cloud-like structure corresponding to the classical nucleolus of polytene chromosomes, as well as an unusual intrachromosomal structure containing alternating transcriptionally active and inactive regions.

KW - Drosophila melanogaster

KW - heterochromatin

KW - In(1)sc

KW - inversion

KW - nucleolus

KW - polytene chromosomes

KW - Rif1

KW - underreplication

KW - Heterochromatin/genetics

KW - Drosophila Proteins/genetics

KW - Drosophila melanogaster/genetics

KW - Repetitive Sequences, Nucleic Acid/genetics

KW - X Chromosome/genetics

KW - Animals

KW - Nucleolus Organizer Region

KW - Carrier Proteins/genetics

KW - In(1)sc8

UR - http://www.scopus.com/inward/record.url?scp=85143657245&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/43bbe341-6604-350f-9232-b3badbc971a9/

U2 - 10.3390/cells11233872

DO - 10.3390/cells11233872

M3 - Article

C2 - 36497131

AN - SCOPUS:85143657245

VL - 11

JO - Cells

JF - Cells

SN - 2073-4409

IS - 23

M1 - 3872

ER -