scholarly journals Distinct Regulation of the Expression of Satellite DNAs in the Beetle Tribolium castaneum

2020 ◽  
Vol 22 (1) ◽  
pp. 296
Author(s):  
Antonio Sermek ◽  
Isidoro Feliciello ◽  
Đurđica Ugarković

In the flour beetle, Tribolium castaneum (peri)centromeric heterochromatin is mainly composed of a major satellite DNA TCAST1 interspersed with minor satellites. With the exception of heterochromatin, clustered satellite repeats are found dispersed within euchromatin. In order to uncover a possible satellite DNA function within the beetle genome, we analysed the expression of the major TCAST1 and a minor TCAST2 satellite during the development and upon heat stress. The results reveal that TCAST1 transcription was strongly induced at specific embryonic stages and upon heat stress, while TCAST2 transcription is stable during both processes. TCAST1 transcripts are processed preferentially into piRNAs during embryogenesis and into siRNAs during later development, contrary to TCAST2 transcripts, which are processed exclusively into piRNAs. In addition, increased TCAST1 expression upon heat stress is accompanied by the enrichment of the silent histone mark H3K9me3 on the major satellite, while the H3K9me3 level at TCAST2 remains unchanged. The transcription of the two satellites is proposed to be affected by the chromatin state: heterochromatin and euchromatin, which are assumed to be the prevalent sources of TCAST1 and TCAST2 transcripts, respectively. In addition, distinct regulation of the expression might be related to diverse roles that major and minor satellite RNAs play during the development and stress response.

Genes ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 663
Author(s):  
Isidoro Feliciello ◽  
Antonio Sermek ◽  
Željka Pezer ◽  
Maja Matulić ◽  
Đurđica Ugarković

Satellite DNAs are tandemly repeated sequences preferentially assembled into large arrays within constitutive heterochromatin and their transcription is often activated by stress conditions, particularly by heat stress. Bioinformatic analyses of sequenced genomes however reveal single repeats or short arrays of satellite DNAs dispersed in the vicinity of genes within euchromatin. Here, we analyze transcription of a major human alpha satellite DNA upon heat stress and follow the dynamics of “silent” H3K9me3 and “active” H3K4me2/3 histone marks at dispersed euchromatic and tandemly arranged heterochromatic alpha repeats. The results show H3K9me3 enrichment at alpha repeats upon heat stress, which correlates with the dynamics of alpha satellite DNA transcription activation, while no change in H3K4me2/3 level is detected. Spreading of H3K9me3 up to 1–2 kb from the insertion sites of the euchromatic alpha repeats is detected, revealing the alpha repeats as modulators of local chromatin structure. In addition, expression of genes containing alpha repeats within introns as well as of genes closest to the intergenic alpha repeats is downregulated upon heat stress. Further studies are necessary to reveal the possible contribution of H3K9me3 enriched alpha repeats, in particular those located within introns, to the silencing of their associated genes.


2015 ◽  
Vol 146 (2) ◽  
pp. 153-170 ◽  
Author(s):  
Manuel A. Garrido-Ramos

For decades, satellite DNAs have been the hidden part of genomes. Initially considered as junk DNA, there is currently an increasing appreciation of the functional significance of satellite DNA repeats and of their sequences. Satellite DNA families accumulate in the heterochromatin in different parts of the eukaryotic chromosomes, mainly in pericentromeric and subtelomeric regions, but they also span the functional centromere. Tandem repeat sequences may spread from subtelomeric to interstitial loci, leading to the formation of chromosome-specific loci or to the accumulation in equilocal sites in different chromosomes. They also appear as the main components of the heterochromatin in the sex-specific region of sex chromosomes. Satellite DNA, required for chromosome organization, also plays a role in pairing and segregation. Some satellite repeats are transcribed and can participate in the formation and maintenance of heterochromatin structure and in the modulation of gene expression. In addition to the identification of the different satellite DNA families, their characteristics and location, we are interested in determining their impact on the genomes, by identifying the mechanisms leading to their appearance and amplification as well as in understanding how they change over time, the factors affecting these changes, and the influence exerted by the evolutionary history of the organisms. On the other hand, satellite DNA sequences are rapidly evolving sequences that may cause reproductive barriers between organisms and promote speciation. The accumulation of experimental data collected in recent years and the emergence of new approaches based on next-generation sequencing and high-throughput genome analysis are opening new perspectives that are changing our understanding of satellite DNA. This review examines recent data to provide a timely update on the overall information gathered about this part of the genome, focusing on the advances in the knowledge of its origin, its evolution, and its potential functional roles.


2019 ◽  
Author(s):  
Tihana Vondrak ◽  
Laura Ávila Robledillo ◽  
Petr Novák ◽  
Andrea Koblížková ◽  
Pavel Neumann ◽  
...  

AbstractBackgroundAmplification of monomer sequences into long contiguous arrays is the main feature distinguishing satellite DNA from other tandem repeats, yet it is also the main obstacle in its investigation because these arrays are in principle difficult to assemble. Here we explore an alternative, assembly-free approach that utilizes ultra-long Oxford Nanopore reads to infer the length distribution of satellite repeat arrays, their association with other repeats and the prevailing sequence periodicities.ResultsWe have developed a computational workflow for similarity-based detection and downstream analysis of satellite repeats in individual nanopore reads that led to genome-wide characterization of their properties. Using the satellite DNA-rich legume plantLathyrus sativusas a model, we demonstrated this approach by analyzing eleven major satellite repeats using a set of nanopore reads ranging from 30 to over 200 kb in length and representing 0.73x genome coverage. We found surprising differences between the analyzed repeats because only two of them were predominantly organized in long arrays typical for satellite DNA. The remaining nine satellites were found to be derived from short tandem arrays located within LTR-retrotransposons that occasionally expanded in length. While the corresponding LTR-retrotransposons were dispersed across the genome, this array expansion occurred mainly in the primary constrictions of theL. sativuschromosomes, which suggests that these genome regions are favorable for satellite DNA accumulation.ConclusionsThe presented approach proved to be efficient in revealing differences in long-range organization of satellite repeats that can be used to investigate their origin and evolution in the genome.


PLoS Genetics ◽  
2015 ◽  
Vol 11 (8) ◽  
pp. e1005466 ◽  
Author(s):  
Isidoro Feliciello ◽  
Ivana Akrap ◽  
Đurđica Ugarković

2021 ◽  
Vol 11 ◽  
Author(s):  
Ljudevit Luka Boštjančić ◽  
Lena Bonassin ◽  
Lucija Anušić ◽  
Leona Lovrenčić ◽  
Višnja Besendorfer ◽  
...  

Pontastacus leptodactylus is a native European crayfish species found in both freshwater and brackish environments. It has commercial importance for fisheries and aquaculture industries. Up till now, most studies concerning P. leptodactylus have focused onto gaining knowledge about its phylogeny and population genetics. However, little is known about the chromosomal evolution and genome organization of this species. Therefore, we performed clustering analysis of a low coverage genomic dataset to identify and characterize repetitive DNA in the P. leptodactylus genome. In addition, the karyogram of P. leptodactylus (2n = 180) is presented here for the first time consisting of 75 metacentric, 14 submetacentric, and a submetacentric/metacentric heteromorphic chromosome pair. We determined the genome size to be at ~18.7 gigabase pairs. Repetitive DNA represents about 54.85% of the genome. Satellite DNA repeats are the most abundant type of repetitive DNA, making up to ~28% of the total amount of repetitive elements, followed by the Ty3/Gypsy retroelements (~15%). Our study established a surprisingly high diversity of satellite repeats in P. leptodactylus. The genome of P. leptodactylus is by far the most satellite-rich genome discovered to date with 258 satellite families described. Of the five mapped satellite DNA families on chromosomes, PlSAT3-411 co-localizes with the AT-rich DAPI positive probable (peri)centromeric heterochromatin on all chromosomes, while PlSAT14-79 co-localizes with the AT-rich DAPI positive (peri)centromeric heterochromatin on one chromosome and is also located subterminally and intercalary on some chromosomes. PlSAT1-21 is located intercalary in the vicinity of the (peri)centromeric heterochromatin on some chromosomes, while PlSAT6-70 and PlSAT7-134 are located intercalary on some P. leptodactylus chromosomes. The FISH results reveal amplification of interstitial telomeric repeats (ITRs) in P. leptodactylus. The prevalence of repetitive elements, especially the satellite DNA repeats, may have provided a driving force for the evolution of the P. leptodactylus genome.


2019 ◽  
Author(s):  
Wilbur K Mills ◽  
Yuh Chwen G. Lee ◽  
Antje M Kochendoerfer ◽  
Elaine M Dunleavy ◽  
Gary H. Karpen

AbstractLong arrays of simple, tandemly repeated DNA sequences (known as satellites) are enriched in centromeres1 and pericentromeric regions2, and contribute to chromosome segregation and other heterochromatin functions3,4. Surprisingly, satellite DNAs are expressed in many multicellular eukaryotes, and their aberrant transcription may contribute to carcinogenesis and cellular toxicity5-7. Satellite transcription and/or RNAs may also promote centromere and heterochromatin activities 8-12. However, we lack direct evidence that satellite DNA transcripts are required for normal cell or organismal functions. Here, we show that satellite RNAs derived from AAGAG tandem repeats are transcribed in many cell types throughout Drosophila melanogaster development, enriched in neuronal tissues and testes, localized within heterochromatic regions, and important for viability. Strikingly, we find that AAGAG transcripts are necessary for male fertility and are specifically required for normal histone-protamine exchange and sperm chromatin organization. Since AAGAG RNA-dependent events happen late in spermatogenesis when the transcripts are not detected, we speculate that AAGAG RNA functions in primary spermatocytes to ‘prime’ post-meiosis steps in sperm maturation. In addition to demonstrating specific essential functions for AAGAG RNAs, comparisons between closely related Drosophila species suggest that satellite repeats and their transcription evolve quickly to generate new functions.


Genetica ◽  
2011 ◽  
Vol 139 (8) ◽  
pp. 999-1008 ◽  
Author(s):  
Isidoro Feliciello ◽  
Gianni Chinali ◽  
Đurđica Ugarković

PLoS Genetics ◽  
2015 ◽  
Vol 11 (9) ◽  
pp. e1005547
Author(s):  
Isidoro Feliciello ◽  
Ivana Akrap ◽  
Đurđica Ugarković

2017 ◽  
Author(s):  
Mirela Pelizaro Valeri ◽  
Guilherme Borges Dias ◽  
Valéria do Socorro Pereira ◽  
Gustavo Campos Silva Kuhn ◽  
Marta Svartman

AbstractSatellite DNAs (satDNAs) are major components of eukaryote genomes. However, because of their quick divergence, the evolutionary origin of a given satDNA family can rarely be determined. Herein we took advantage of available primate sequenced genomes to determine the origin of the CapA satDNA (~1,500 bp long monomers), first described in Sapajus apella. We show that CapA is an abundant satDNA in Platyrrhini, whereas in the genomes of most eutherian mammals, including humans, this sequence is present only as a single copy located within a large intron of the NOS1AP (nitric oxid synthase 1 adaptor protein) Gene. Our data suggest that this intronic CapA-like sequence gave rise to the CapA satDNA and we discuss possible mechanisms implicated in this event. This is the first report of a single copy intronic sequence giving origin to a satDNA that reaches up to 100,000 copies in some genomes.


Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 333-341
Author(s):  
W Stephan ◽  
S Cho

Abstract A simulation model of sequence-dependent amplification, unequal crossing over and mutation is analyzed. This model predicts the spontaneous formation of tandem-repetitive patterns of noncoding DNA from arbitrary sequences for a wide range of parameter values. Natural selection is found to play an essential role in this self-organizing process. Natural selection which is modeled as a mechanism for controlling the length of a nucleotide string but not the sequence itself favors the formation of tandem-repetitive structures. Two measures of sequence heterogeneity, inter-repeat variability and repeat length, are analyzed in detail. For fixed mutation rate, both inter-repeat variability and repeat length are found to increase with decreasing rates of (unequal) crossing over. The results are compared with data on micro-, mini- and satellite DNAs. The properties of minisatellites and satellite DNAs resemble the simulated structures very closely. This suggests that unequal crossing over is a dominant long-range ordering force which keeps these arrays homogeneous even in regions of very low recombination rates, such as at satellite DNA loci. Our analysis also indicates that in regions of low rates of (unequal) crossing over, inter-repeat variability is maintained at a low level at the expense of much larger repeat units (multimeric repeats), which are characteristic of satellite DNA. In contrast, the microsatellite data do not fit the proposed model well, suggesting that unequal crossing over does not act on these very short tandem arrays.


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