Histone H1 expression varies during the Leishmania major life cycle.

The deduced amino acid sequence of Leishmania major sw3 cDNA reveals the presence of characteristic histone H1 amino acid motifs. However, the open reading frame is of an unusually small size for histone H1 (105 amino acids) because it lacks the coding potential for the central hydrophobic globular domain of linker histones present in other eukaryotes. Here, we provide biochemical evidence that the SW3 protein is indeed a L. major nuclear histone H1, and that it is differentially expressed during the life cycle of the parasite. Due to its high lysine content, the SW3 protein can be purified to a high degree from L. major nuclear lysates with 5% perchloric acid, a histone H1 preparative method. Using an anti-SW3 antibody, this protein is detected as a 17 kDa or as a 17/19 kDa doublet in the nuclear subfraction in different L. major strains. The nuclear localization of the SW3 protein is further supported by immunofluorescence studies. During in vitro promastigote growth, both the sw3 cytoplasmic mRNA and its protein progressively accumulate within parasites from early log phase to stationary phase. Within amastigotes, the high level of H1 expression is maintained but decreases when amastigotes differentiate into promastigotes. Together, these observations suggest that the different levels of this histone H1 protein could influence the varying degrees of chromatin condensation during the life-cycle of the parasite, and provide us with tools to study this mechanism

Sense and antisense transcripts in the histone H1 (HIS-1) locus of Leishmania major.

Histone H1 in the parasitic protozoan Leishmania is a developmentally regulated protein encoded by two genes, HIS-1.1 and HIS-1.2. These genes are separated by approximately 20 kb of sequence and are located on the same DNA strand of chromosome 27. When Northern blots of parasite RNA were probed with HIS-1 strand-specific riboprobes, we detected sense and antisense transcripts that were polyadenylated and developmentally regulated. When the HIS-1.2 coding region was replaced with the coding region of the neomycin phosphotransferase gene, antisense transcription of this gene was unaffected, indicating that the regulatory elements controlling antisense transcription were located outside of the HIS-1.2 gene, and that transcription in Leishmania can occur from both DNA strands even in the presence of transcription of a selectable marker in the complementary strand. A search for other antisense transcripts within the HIS-1 locus identified an additional transcript (SC-1) within the intervening HIS-1 sequence, downstream of adenine and thymine-rich sequences. These results show that gene expression in Leishmania is not only regulated polycistronically from the sense strand of genomic DNA, but that the complementary strand of DNA also contains sequences that could drive expression of open reading frames from the antisense strand of DNA. These findings suggest that the parasite has evolved in such a way as to maximise the transcription of its genome, a mechanism that might be important for it to maintain virulence

Double beta decay of 150^{150}Nd to the first 0+^+ excited level of 150^{150}Sm

International audienceAn experiment to measure the 2$\beta{^-}$ decay of $^{150}$Nd to excited levels of $^{150}$Sm using a highly purified 2.381 kg sample of Nd$_2$O$_3$ is in progress in the low-background set-up with 4 HPGe detectors (~225 cm$^3$ volume each). The detector is located deep underground (3600 m w.e.) at the STELLA facility of the Gran Sasso National Laboratory (LNGS) of the INFN (Italy). Two γ quanta with energies 334.0 keV and 406.5 keV emitted after deexcitation of the 0$_1 {^+}$ excited level of 1$^{50S}$m have been observed in the experimental data accumulated over 39898 h. The preliminary half-life value for 2$\beta{^-}$ decay of $^{150}$Nd to the first 0$^+$ excited level in $^{150}$Sm (after the exposure of 10.8 kg $\times$ yr) was estimated as $T_{1/2}=[9.7{{+2.9}\atop{-1.9}}(stat.) {\pm}1.5(syst.)]\times 10^{19}$ yr. The experiment is under data taking with the aim to improve the statistical uncertainties

Search for double beta decay of 116^{116}Cd with enriched 116^{116}CdWO4_4 crystal scintillators (Aurora experiment)

International audienceThe Aurora experiment to investigate double beta decay of (116) Cd with the help of 1.162 kg cadmium tungstate crystal scintillators enriched in (116) Cd to 82% is in progress at the Gran Sasso Underground Laboratory. The half-life of (116) Cd relatively to the two neutrino double beta decay is measured with the highest up-to-date accuracy T(1/2) = (2.62 ± 0.14) × 10(19) yr. The sensitivity of the experiment to the neutrinoless double beta decay of (116) Cd to the ground state of (116) Sn is estimated as T(1/2) ≥ 1.9 × 10(23) yr at 90% CL, which corresponds to the effective Majorana neutrino mass limit (mv) ≤ (1.2 — 1.8) eV. New limits are obtained for the double beta decay of (116) Cd to the excited levels of (116) Sn, and for the neutrinoless double beta decay with emission of majorons

Double beta decay of 150^{150}Nd to the first excited 0+^{+} level of 150^{150}Sm: Preliminary results

International audienceThe double beta decay of 150Nd to the first excited 0+ level of 150Sm (Eexc = 740.5 keV) was investigated with the help of the ultra-low-background setup consisting of four HP Ge (high-purity germanium) detectors (≃225 cm3 volume each one) at the Gran Sasso underground laboratory of INFN (Italy). A highly purified 2.381-kg sample of neodymium oxide (Nd2O3) was used as a source of γ quanta expected in the decays. Gamma quanta with energies 334.0 keV and 406.5 keV emitted after deexcitation of the 01+ 740.5 keV excited level of 150Sm are observed in the coincidence spectra accumulated over 16375 h. The half-life relatively to the two neutrino double beta decay 150Nd → 150Sm(01+) is measured as T1/2 = [4.7+4.1-1.9(stat)±0.5(syst)]×1019 y, in agreement with results of previous experiments

Final results of the Aurora experiment to study 2β2\beta decay of 116Cd^{116}\mathrm{Cd} with enriched 116CdWO4^{116}\mathrm{Cd}{\mathrm{WO}}_{4} crystal scintillators

International audienceThe double-beta decay of Cd116 has been investigated with the help of radiopure enriched Cd116WO4 crystal scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory. The half-life of Cd116 relative to the 2ν2β decay to the ground state of Sn116 was measured with the highest up-to-date accuracy as T1/2=(2.63-0.12+0.11)×1019  yr. A new improved limit on the 0ν2β decay of Cd116 to the ground state of Sn116 was set as T1/2≥2.2×1023  yr at 90% C.L., which is the most stringent known restriction for this isotope. It corresponds to the effective Majorana neutrino mass limit in the range ⟨mν⟩≤(1.0–1.7)  eV, depending on the nuclear matrix elements used in the estimations. New improved half-life limits for the 0ν2β decay with majoron(s) emission, Lorentz-violating 2ν2β decay, and 2β transitions to excited states of Sn116 were set at the level of T1/2≥1020–1022  yr. New limits for the hypothetical lepton-number violating parameters (right-handed currents admixtures in weak interaction, the effective majoron-neutrino coupling constants, R-parity violating parameter, Lorentz-violating parameter, heavy neutrino mass) were set

Recent Results on the Search for 2β Decay Processes With Scintillators and Pure Samples

Some recent results obtained in the search for double beta decay in various isotopes obtained in experiments carried out at LNGS with the DAMA/R&D, DAMA/Ge set-up and the STELLA facility will be summarized