Helicase Q promotes homology-driven DNA double-strand break repair and prevents tandem duplications.

DNA double-strand breaks are a major threat to cellular survival and genetic integrity. In addition to high fidelity repair, three intrinsically mutagenic DNA break repair routes have been described, i.e. single-strand annealing (SSA), polymerase theta-mediated end-joining (TMEJ) and residual ill-defined microhomology-mediated end-joining (MMEJ) activity. Here, we identify C. elegans Helicase Q (HELQ-1) as being essential for MMEJ as well as for SSA. We also find HELQ-1 to be crucial for the synthesis-dependent strand annealing (SDSA) mode of homologous recombination (HR). Loss of HELQ-1 leads to increased genome instability: patchwork insertions arise at deletion junctions due to abortive rounds of polymerase theta activity, and tandem duplications spontaneously accumulate in genomes of helq-1 mutant animals as a result of TMEJ of abrogated HR intermediates. Our work thus implicates HELQ activity for all DSB repair modes guided by complementary base pairs and provides mechanistic insight into mutational signatures common in HR-defective cancers.

Tamponade due to Rhodococcus equi in acquired immunodeficiency syndrome.

Infection with Rhodococcus equi has been described as a cause of cavitary pneumonia in AIDS patients. We report such a case, complicated by bacteremia, tamponade, and possible brain and liver abscesses. Medical treatment was successful with pericardiocentesis and antibiotherapy with teicoplanin, gentamicin, clarithromycin, rifampicin, supplemented by empirical treatment of cerebral toxoplasmosis. Antibiotherapy was terminated after 6 months, without relapse 2 months later.

[Angiosarcoma of the aorta disclosed by intestinal metastasis]. / Angiosarcome de l'aorte révélé par une métastase intestinale.

The authors report a case of angiosarcoma of the descending thoracic aorta presenting with a metastasis of the small intestine. This is a very rare tumour in this localisation, two cases having been described among the 28 cases of aortic tumour reported in the literature.

[Pulmonary malacoplakia and Rhodococcus equi pneumonia in a patient infected with the human immunodeficiency virus. A case report with review of the literature]. / Malacoplasie pulmonaire et pneumonie à Rhodococcus equi chez un patient infecté par le virus de l'immunodépression humaine. A propos d'un cas avec revue de la littérature.

We report a case of pulmonary malakoplakia in a patient suffering from AIDS secondary to a Rhodococcus equi pneumonia. The association between these two pathologies only occurring in the immunodepressed does not seen fortuitous. Deficiency in cellular immunity and macrophage cellular activity as well as failure of intracellular bactericidal and phagolysosomal function are very probably the links. The treatment of this opportunistic germ rests on prolonged poly-antibiotic therapy or indeed surgical excision.

[Disappearance of emphysematous bullae after infectious episodes]. / Disparition de bulles d'emphysème après épisodes infectieux.

The authors report 3 cases of peri-emphysematous lung infection associated with the development of air-fluid level in pre-existing emphysematous bullae. Prolonged observation revealed that both bullae and fluid disappeared completely or partially after short antibiotic treatment. The review of literature show that this favourable evolution has not often been described and that these pictures must be to differentiate from lung abscess.