Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Stretches of guanines can associate in vitro through Hoogsteen hydrogen bonding to form four-stranded structures. In the HIV-1 central DNA flap, generated by reverse transcriptase at the end of retrotranscription, both the two 99 nt-long overlapping (+) strands contain two adjacent tracts of guanines. This study demonstrates that oligonucleotides containing these G-clusters form highly stable G-quadruplexes of various structures in vitro, whose formation was controlled by an easy and reversible protocol using sodium hydroxide. Among these sequences, a G'2 hairpin dimer was the most stable structure adopted by the 5'-tail of the (+) downstream strand. Since the two (+) strands of the HIV-1 central DNA flap hold these G-clusters, and based on the properties of reverse branch migration in DNA flaps, constructions using HIV-1 sequences were assembled to mimic small DNA flaps where the G-clusters are neighbors. G-quartets were successfully probed in such flaps. They were induced by potassium and by a dibenzophenanthroline derivative already known to stabilize them. Such results suggest some function(s) for G-quartets associated with a DNA flap in the HIV-1 pre-integration steps, and argue for their transient formation during the processing of G-rich DNA flaps at the time of replication and/or repair.
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PMID:G-quartets assembly within a G-rich DNA flap. A possible event at the center of the HIV-1 genome. 1246 53

As an accompanying manuscript to the release of the honey bee genome, we report the entire sequence of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) ribosomal RNA (rRNA)-encoding gene sequences (rDNA) and related internally and externally transcribed spacer regions of Apis mellifera (Insecta: Hymenoptera: Apocrita). Additionally, we predict secondary structures for the mature rRNA molecules based on comparative sequence analyses with other arthropod taxa and reference to recently published crystal structures of the ribosome. In general, the structures of honey bee rRNAs are in agreement with previously predicted rRNA models from other arthropods in core regions of the rRNA, with little additional expansion in non-conserved regions. Our multiple sequence alignments are made available on several public databases and provide a preliminary establishment of a global structural model of all rRNAs from the insects. Additionally, we provide conserved stretches of sequences flanking the rDNA cistrons that comprise the externally transcribed spacer regions (ETS) and part of the intergenic spacer region (IGS), including several repetitive motifs. Finally, we report the occurrence of retrotransposition in the nuclear large subunit rDNA, as R2 elements are present in the usual insertion points found in other arthropods. Interestingly, functional R1 elements usually present in the genomes of insects were not detected in the honey bee rRNA genes. The reverse transcriptase products of the R2 elements are deduced from their putative open reading frames and structurally aligned with those from another hymenopteran insect, the jewel wasp Nasonia (Pteromalidae). Stretches of conserved amino acids shared between Apis and Nasonia are illustrated and serve as potential sites for primer design, as target amplicons within these R2 elements may serve as novel phylogenetic markers for Hymenoptera. Given the impending completion of the sequencing of the Nasonia genome, we expect our report eventually to shed light on the evolution of the hymenopteran genome within higher insects, particularly regarding the relative maintenance of conserved rDNA genes, related variable spacer regions and retrotransposable elements.
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PMID:Characteristics of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) rRNA genes of Apis mellifera (Insecta: Hymenoptera): structure, organization, and retrotransposable elements. 1706 39