Conserved Secondary Structures in Aspergillus

Background: Recent evidence suggests that the number and variety of functional RNAs (ncRNAs as well as cis-acting RNA elements within mRNAs) is much higher than previously thought; thus, the ability to computationally predict and analyze RNAs has taken on new importance. We have computationally studied the secondary structures in an alignment of six Aspergillus genomes. Little is known about the RNAs present in this set of fungi, and this diverse set of genomes has an optimal level of sequence conservation for observing the correlated evolution of base-pairs seen in RNAs. Methodology/Principal Findings: We report the results of a whole-genome search for evolutionarily conserved secondary structures, as well as the results of clustering these predicted secondary structures by structural similarity. We find a total of 7450 predicted secondary structures, including a new predicted,60 bp long hairpin motif found primarily inside introns. We find no evidence for microRNAs. Different types of genomic regions are over-represented in different classes of predicted secondary structures. Exons contain the longest motifs (primarily long, branched hairpins), 59 UTRs primarily contain groupings of short hairpins located near the start codon, and 39 UTRs contain very little secondary structure compared to other regions. There is a large concentration of short hairpins just inside the boundaries of exons. The density of predicted intronic RNAs increases with the length of introns, and the density of predicted secondary structures within mRNA coding regions increases with the number of introns in a gene

Mechanism of Splicing Regulation of Spinal Muscular Atrophy Genes

Spinal muscular atrophy (SMA) is one of the major genetic disorders associated with infant mortality. More than 90% cases of SMA result from deletions or mutations of Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, does not compensate for the loss of SMN1due to predominant skipping of exon 7. However, correction of SMN2 exon 7 splicing has proven to confer therapeutic benefits in SMA patients. The only approved drug for SMA is an antisense oligonucleotide (Spinraza™/Nusinersen), which corrects SMN2 exon 7 splicing by blocking intronic splicing silencer N1 (ISS-N1) located immediately downstream of exon 7. ISS-N1 is a complex regulatory element encompassing overlapping negative motifs and sequestering a cryptic splice site. More than 40 protein factors have been implicated in the regulation of SMN exon 7 splicing. There is evidence to support that multiple exons of SMN are alternatively spliced during oxidative stress, which is associated with a growing number of pathological conditions. Here, we provide the most up to date account of the mechanism of splicing regulation of the SMN genes

Surgical Control of a Primary Hepatic Carcinoid Tumor: A Case Report

We report a primary hepatic carcinoid tumor occurring in a 47-year-old man. The patient consulted our hospital complaining of epigastralgia. Abdominal ultrasonography, computed tomography scanning, and magnetic resonance imaging showed a large mass in the right lobe of the liver. FDG-PET revealed 18F-FDG uptake by the right hepatic lobe. The tumor was a solid mass with cystic components, approximately 15 cm in diameter. We conducted an extended right lobectomy of the liver. The resected specimen was a solid tumor with cystic components and hemorrhagic lesion. Microscopic findings showed that the tumor cells had round nuclei and formed trabecular patterns. Immunohistologically, tumor cells were stained positive for chromogranin A, neuron specific enolase, CD56, and S-100. Careful examinations before and after the operation revealed no other possible origin of the tumor. Based on these findings, the tumor was diagnosed as a primary hepatic carcinoid. This is a report of a rare case of a primary hepatic carcinoid tumor with a discussion of several other relevant reports

Acquisition of inverted GSTM exons by an intron of primate GSTM5 gene

The human GSTM gene family is composed of five gene members, GSTM1-5, and plays an important role in detoxification. In this study, the human GSTM5 gene was found to have a long inverted repeat (LIR) in intron 5. The LIR is able to form a stem-loop structure with a 31-bp stem and a 9-nt loop. The intronic LIR was also identified in other primates but not in non-primates. The human and chimpanzee LIRs had undergone compensating mutations that make the stem loop more stable, suggesting a functional role for the LIR. Sequence homology showed that the LIR was actually a part of inverted exons acquired by the intron. Results of phylogenetic analysis indicate that the inverted exons were derived from exon 5 of GSTM4 and exon 5 of GSTM1. The intronic LIR and inverted GSTM exons can probably introduce complexity in the expression of GSTM gene family. © 2009 The Japan Society of Human Genetics. All rights reserved.link_to_subscribed_fulltex