rDNA and Nucleologenesis in Drosophila

James, Allison; Raje, Himanshu

doi:10.1007/978-94-007-5818-6_3

Cited by 4 publications

(4 citation statements)

References 173 publications

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“…Drosophila provides an attractive model for studying the transcriptional regulation at the level of individual rDNA units because some rRNA genes in this organism are marked by insertions of non-LTR retrotransposons called R1 and R2 (see ( 30 , 31 ) for reviews). In D. melanogaster , rDNA clusters located in the X and Y chromosomes usually consist of 200–250 rDNA units ( 32 ), more than half of which contain insertions.…”

Section: Introductionmentioning

confidence: 99%

Impaired function of rDNA transcription initiation machinery leads to derepression of ribosomal genes with insertions of R2 retrotransposon

Fefelova

Pleshakova

Mikhaleva

et al. 2022

Nucleic Acids Research

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Eukaryotic genomes harbor hundreds of rRNA genes, many of which are transcriptionally silent. However, little is known about selective regulation of individual rDNA units. In Drosophila melanogaster, some rDNA repeats contain insertions of the R2 retrotransposon, which is capable to be transcribed only as part of pre-rRNA molecules. rDNA units with R2 insertions are usually inactivated, although R2 expression may be beneficial in cells with decreased rDNA copy number. Here we found that R2-inserted rDNA units are enriched with HP1a and H3K9me3 repressive mark, whereas disruption of the heterochromatin components slightly affects their silencing in ovarian germ cells. Surprisingly, we observed a dramatic upregulation of R2-inserted rRNA genes in ovaries lacking Udd (Under-developed) or other subunits (TAF1b and TAF1c-like) of the SL1-like complex, which is homologues to mammalian Selective factor 1 (SL1) involved in rDNA transcription initiation. Derepression of rRNA genes with R2 insertions was accompanied by a reduction of H3K9me3 and HP1a enrichment. We suggest that the impairment of the SL1-like complex affects a mechanism of selective activation of intact rDNA units which competes with heterochromatin formation. We also propose that R2 derepression may serve as an adaptive response to compromised rRNA synthesis.

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Section: Introductionmentioning

confidence: 99%

Impaired function of rDNA transcription initiation machinery leads to derepression of ribosomal genes with insertions of R2 retrotransposon

Fefelova

Pleshakova

Mikhaleva

et al. 2022

Nucleic Acids Research

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“…Previous attempts to establish a consensus for NoLSs have not been successful [50][51][52]. However, it is known that NoLS motifs usually contain stretches of positively charged amino acid residues such as lysine (K), arginine (R), and histidine (H) [53]. The positive charge is believed to induce protein accumulation in the nucleolus, according to the electrostatic hypothesis [53].…”

Section: Nols Motifs From Drosophila Nucleolus Proteinsmentioning

confidence: 99%

“…However, it is known that NoLS motifs usually contain stretches of positively charged amino acid residues such as lysine (K), arginine (R), and histidine (H) [53]. The positive charge is believed to induce protein accumulation in the nucleolus, according to the electrostatic hypothesis [53]. As a result, NoLS motifs were predicted in different regions of the Non3, Pit, NS1, NS3, and Mod proteins (Figure 3, Table 1).…”

Section: Nols Motifs From Drosophila Nucleolus Proteinsmentioning

confidence: 99%

“…This might be because some proteins that concentrate in the nucleolus lack a well-defined NoLS motif [54,55], or because other NoLS-containing proteins facilitate their recruitment to the nucleolus [42,56]. that NoLS motifs usually contain stretches of positively charged amino acid residues such as lysine (K), arginine (R), and histidine (H) [53]. The positive charge is believed to induce protein accumulation in the nucleolus, according to the electrostatic hypothesis [53].…”

Section: Nols Motifs From Drosophila Nucleolus Proteinsmentioning

confidence: 99%

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New Functional Motifs for the Targeted Localization of Proteins to the Nucleolus in Drosophila and Human Cells

Ogienko,

Korepina,

Pindyurin

et al. 2024

IJMS

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The nucleolus is a significant nuclear organelle that is primarily known for its role in ribosome biogenesis. However, emerging evidence suggests that the nucleolus may have additional functions. Particularly, it is involved in the organization of the three-dimensional structure of the genome. The nucleolus acts as a platform for the clustering of repressed chromatin, although this process is not yet fully understood, especially in the context of Drosophila. One way to study the regions of the genome that cluster near the nucleolus in Drosophila demands the identification of a reliable nucleolus-localizing signal (NoLS) motif(s) that can highly specifically recruit the protein of interest to the nucleolus. Here, we tested a series of various NoLS motifs from proteins of different species, as well as some of their combinations, for the ability to drive the nucleolar localization of the chimeric H2B-GFP protein. Several short motifs were found to effectively localize the H2B-GFP protein to the nucleolus in over 40% of transfected Drosophila S2 cells. Furthermore, it was demonstrated that NoLS motifs derived from Drosophila proteins exhibited greater efficiency compared to that of those from other species.

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Role of Udd protein and heterochromatin in transcriptional selection of individual rRNA genes in theDrosophilagermline

Fefelova

Pleshakova

Pirogov

et al. 2020

Preprint

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Eukaryotic genomes contain hundreds of nearly identical rRNA genes, many of which are transcriptionally silent. However, the mechanisms of selective regulation of individual rDNA units remain poorly understood. In Drosophila melanogaster, rDNA repeats containing insertions of R1/R2 retrotransposons within the 28S rRNA sequence undergo inactivation. Here we found that rRNA genes with insertions are specifically enriched with H3K9me3 and HP1a repressive marks, but disruption of heterochromatin components only slightly affects their silencing. Intriguingly, the loss of Udd (Under-developed) protein interacting with Pol I transcription initiation complex, causes an upregulation of R2-inserted rDNA copies in germ cells by two orders of magnitude that is accompanied by the reduction of heterochromatin marks. Thus, for the first time we revealed a factor required for distinguishing between active and silent rDNA units to such a large extent. To clarify a relationship between the rDNA transcriptional status and heterochromatin establishment, we showed that inhibition of transcription by actinomycin D increases the level of H3K9me3 mark erasing the epigenetic differences between inserted and uninserted rRNA genes. Altogether, we suggest that Udd coupled with Pol I transcription initiation machinery defines activation or silencing of individual rDNA units, whereas their transcription level consequently dictates their chromatin state.

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rDNA and Nucleologenesis in Drosophila

Cited by 4 publications

References 173 publications

Impaired function of rDNA transcription initiation machinery leads to derepression of ribosomal genes with insertions of R2 retrotransposon

Impaired function of rDNA transcription initiation machinery leads to derepression of ribosomal genes with insertions of R2 retrotransposon

New Functional Motifs for the Targeted Localization of Proteins to the Nucleolus in Drosophila and Human Cells

Role of Udd protein and heterochromatin in transcriptional selection of individual rRNA genes in theDrosophilagermline

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