Rodrigo Yelin

Widespread occurrence of antisense transcription in the human genome

An increasing number of eukaryotic genes are being found to have naturally occurring antisense transcripts. Here we study the extent of antisense transcription in the human genome by analyzing the public databases of expressed sequences using a set of computational tools designed to identify sense-antisense transcriptional units on opposite DNA strands of the same genomic locus. The resulting data set of 2,667 sense-antisense pairs was evaluated by microarrays containing strand-specific oligonucleotide probes derived from the region of overlap. Verification of specific cases by northern blot analysis with strand-specific riboprobes proved transcription from both DNA strands. We conclude that ≥60% of this data set, or ∼1,600 predicted sense-antisense transcriptional units, are transcribed from both DNA strands. This indicates that the occurrence of antisense transcription, usually regarded as infrequent, is a very common phenomenon in the human genome. Therefore, antisense modulation of gene expression in human cells may be a common regulatory mechanism.

Systematic identification of abundant A-to-I editing sites in the human transcriptome

RNA editing by members of the ADAR (adenosine deaminases acting on RNA) family leads to site-specific conversion of adenosine to inosine (A-to-I) in precursor messenger RNAs. Editing by ADARs is believed to occur in all metazoa, and is essential for mammalian development. Currently, only a limited number of human ADAR substrates are known, whereas indirect evidence suggests a substantial fraction of all pre-mRNAs being affected. Here we describe a computational search for ADAR editing sites in the human transcriptome, using millions of available expressed sequences. We mapped 12,723 A-to-I editing sites in 1,637 different genes, with an estimated accuracy of 95%, raising the number of known editing sites by two orders of magnitude. We experimentally validated our method by verifying the occurrence of editing in 26 novel substrates. A-to-I editing in humans primarily occurs in noncoding regions of the RNA, typically in Alu repeats. Analysis of the large set of editing sites indicates the role of editing in controlling dsRNA stability.

Cloning and characterization of a novel human gene RNF38 encoding a conserved putative protein with a RING finger domain.

RING finger (C3HC4-type zinc finger) is a variant zinc finger motif present in a large family of functionally distinct proteins. We describe the cloning and characterization of a novel human transcript RNF38 encoding a new member of the RING finger protein family. The complete mRNA consists of about 6.8 kb widely expressed in human tissues as a single transcript, most abundantly in testis. The predicted proline-rich protein consists of 432 amino acid residues with a coiled-coil motif and a RING-H2 motif (C3H2C2) at its carboxy-terminus. High degree homology was found between the human protein and hypothetical peptides from several other species including Rattus norvegicus, Mus musculus, and Drosophila melanogaster, indicating a significant conservation throughout evolution. The RNF38 genomic structure was determined and comprises at least 13 exons extending over more than 65 kb in the genome, 78 kb centromeric to the GNE gene on human chromosome 9p12-p13. The involvement of this chromosomal segment in a large number of human diseases and in particular in various types of malignancies urges the assessment of the potential functional role of RNF38 in these disorders.