Identification of 18 new transcribed retrotransposons in Schistosoma mansoni.

This work describes 18 new transcribed retrotransposons of the blood fluke Schistosoma mansoni. Among them, 9 were LTR, 8 non-LTR, and 1 Penelope-like element (PLE) retrotransposon. Sequences were generated by in silico reconstruction using S. mansoni ESTs and transcripts obtained by rapid amplification of cDNA ends, complemented in some cases by sequencing of genomic clones amplified by PCR. A novel element from the ancient R2/R4/CRE transposon group is described for the first time in S. mansoni. In addition, one non-LTR retrotransposon family displays long (40-450 bp) 3'-UTR with at least six different transcribed sequences among the copies, five LTR retrotransposons have abundantly transcribed incomplete copies lacking the sequence segment coding for the reverse transcriptase domain, and four non-LTR retrotransposons code for DNA-binding PHD domains that may give them a differential targeting. These results allow for a comprehensive description of the transcribed retrotransposon diversity of this complex human parasite.

Large-scale transcriptome analyses reveal new genetic marker candidates of head, neck, and thyroid cancer.

A detailed genome mapping analysis of 213,636 expressed sequence tags (EST) derived from nontumor and tumor tissues of the oral cavity, larynx, pharynx, and thyroid was done. Transcripts matching known human genes were identified; potential new splice variants were flagged and subjected to manual curation, pointing to 788 putatively new alternative splicing isoforms, the majority (75%) being insertion events. A subset of 34 new splicing isoforms (5% of 788 events) was selected and 23 (68%) were confirmed by reverse transcription-PCR and DNA sequencing. Putative new genes were revealed, including six transcripts mapped to well-studied chromosomes such as 22, as well as transcripts that mapped to 253 intergenic regions. In addition, 2,251 noncoding intronic RNAs, eventually involved in transcriptional regulation, were found. A set of 250 candidate markers for loss of heterozygosis or gene amplification was selected by identifying transcripts that mapped to genomic regions previously known to be frequently amplified or deleted in head, neck, and thyroid tumors. Three of these markers were evaluated by quantitative reverse transcription-PCR in an independent set of individual samples. Along with detailed clinical data about tumor origin, the information reported here is now publicly available on a dedicated Web site as a resource for further biological investigation. This first in silico reconstruction of the head, neck, and thyroid transcriptomes points to a wealth of new candidate markers that can be used for future studies on the molecular basis of these tumors. Similar analysis is warranted for a number of other tumors for which large EST data sets are available.

Antisense intronic non-coding RNA levels correlate to the degree of tumor differentiation in prostate cancer.

A large fraction of transcripts are expressed antisense to introns of known genes in the human genome. Here we show the construction and use of a cDNA microarray platform enriched in intronic transcripts to assess their biological relevance in pathological conditions. To validate the approach, prostate cancer was used as a model, and 27 patient tumor samples with Gleason scores ranging from 5 to 10 were analyzed. We find that a considerably higher fraction (6.6%, [23/346]) of intronic transcripts are significantly correlated (P< or =0.001) to the degree of prostate tumor differentiation (Gleason score) when compared to transcripts from unannotated genomic regions (1%, [6/539]) or from exons of known genes (2%, [27/1369]). Among the top twelve transcripts most correlated to tumor differentiation, six are antisense intronic messages as shown by orientation-specific RT-PCR or Northern blot analysis with strand-specific riboprobe. Orientation-specific real-time RT-PCR with six tumor samples, confirmed the correlation (P=0.024) between the low/high degrees of tumor differentiation and antisense intronic RASSF1 transcript levels. The need to use intron arrays to reveal the transcriptome profile of antisense intronic RNA in cancer has clearly emerged.

Saci-1, -2, and -3 and Perere, four novel retrotransposons with high transcriptional activities from the human parasite Schistosoma mansoni.

Using the data set of 180,000 expressed sequence tags (ESTs) of the blood fluke Schistosoma mansoni generated recently by our group, we identified three novel long-terminal-repeat (LTR)- and one novel non-LTR-expressed retrotransposon, named Saci-1, -2, and -3 and Perere, respectively. Full-length sequences were reconstructed from ESTs and have deduced open reading frames (ORFs) with several uncorrupted features, characterizing them as possible active retrotransposons of different known transposon families. Alignment of reconstructed sequences to available preliminary genome sequence data confirmed the overall structure of the transposons. The frequency of sequenced transposon transcripts in cercariae was 14% of all transcripts from that stage, twofold higher than that in schistosomula and three- to fourfold higher than that in adults, eggs, miracidia, and germ balls. We show by Southern blot analysis, by EST annotation and tallying, and by counting transposon tags from a Serial Analysis of Gene Expression library, that the four novel retrotransposons exhibit a 10- to 30-fold lower copy number in the genome and a 4- to 200-fold-higher transcriptional rate per copy than the four previously described S. mansoni retrotransposons [corrected]. Such differences lead us to hypothesize that there are two different populations of retrotransposons in S. mansoni genome, occupying different niches in its ecology. Examples of retrotransposon fragment inserts were found into the 5' and 3' untranslated regions of four different S. mansoni target gene transcripts. The data presented here suggest a role for these elements in the dynamics of this complex human parasite genome.

Zerg: a very fast BLAST parser library.

SUMMARY: Zerg is a library of sub-routines that parses the output from all NCBI BLAST programs (Blastn, Blastp, Blastx, Tblastn and Tblastx) and returns the attributes of a BLAST report to the user. It is optimized for speed, being especially useful for large-scale genomic analysis. Benchmark tests show that Zerg is over two orders of magnitude faster than some widely used BLAST parsers. AVAILABILITY: http://bioinfo.iq.usp.br/zerg