Helix-hairpin-helix protein MJ1434 from Methanocaldococcus jannaschii and EndoIV homologue TTC0482 from Thermus thermophilus HB27 do not process DNA uracil residues.

The mutagenic threat of hydrolytic DNA cytosine deamination is met mostly by uracil DNA glycosylases (UDG) initiating base excision repair. However, several sequenced genomes of archaeal organisms are devoid of genes coding for homologues of the otherwise ubiquitous UDG superfamily of proteins. Previously, two possible solutions to this problem were offered by (i) a report of a newly discovered family of uracil DNA glycosylases exemplified by MJ1434, a protein found in the hyperthermophilic archaeon Methanocaldococcus jannaschii, and (ii) the description of TTC0482, an EndoIV homologue from the hyperthermophilic bacterium Thermus thermophilus HB27, as being able to excise uracil from DNA. Sequence homologues of both proteins can be found throughout the archaeal domain of life. Three proteins orthologous to MJ1434 and the family founder itself were tested for but failed to exhibit DNA uracil glycosylase activity when produced in an Ung-deficient Escherichia coli host. Likewise, no DNA uracil processing activity could be detected to be associated with TTC0482, while the protein was fully active as an AP endonuclease. We propose that the uracil processing activities formerly found were due to contaminations with Ung enzyme. Use of Deltaung-strains as hosts for production of putatively DNA-U processing enzymes provides a simple safeguard.

Dysregulation of microRNAs in angioimmunoblastic T-cell lymphoma.

BACKGROUND: Angioimmunoblastic T-cell lymphomas (AITLs) are the second most frequent peripheral T-cell lymphomas in humans worldwide and histomorphologically well characterized. MicroRNAs are a group of small non-coding RNAs that can negatively regulate gene expression on a posttranscriptional level. Their dysregulation has been shown to be of importance in numerous tumour entities. MATERIALS AND METHODS: As a first step towards understanding the possible influence of microRNA-dysregulation in AITL, we analyzed the expression signatures of 760 microRNAs in 30 nodal AITLs in comparison to reactive lymphadenitis with T-zone hyperplasia. RESULTS: We found miR-34a, miR-146a and miR-193b to be up-regulated, as well as miR-140-3p, let-7g, miR-30b and miR-664 to be down-regulated in AITL to a significant level. CONCLUSION: The microRNA-signatures of AITL reveal some overlap to autoimmune diseases, virus-triggered lymphomas and angiogenic factors that, coupled with future studies, will potentially provide better understanding of this disease.