Asymmetrical effects of deafness-associated mitochondrial DNA 7516delA mutation on the processing of RNAs in the H-strand and L-strand polycistronic transcripts

In this report, we investigated the molecular mechanism underlying a deafness-associated m.7516delA mutation affecting the 5′ end processing sites of mitochondrial tRNAAsp and tRNASer(UCN). An in vitro processing experiment demonstrated that m.7516delA mutation caused the aberrant 5′ end processing of tRNASer(UCN) and tRNAAsp precursors, catalyzed by RNase P. Using cytoplasmic hybrids (cybrids) derived from one hearing-impaired Chinese family bearing the m.7516delA mutation and control, we demonstrated the asymmetrical effects of m.7516delA mutation on the processing of tRNAs in the heavy (H)-strand and light (L)-strand polycistronic transcripts. Specially, the m.7516delA mutation caused the decreased levels of tRNASer(UCN) and downstream five tRNAs, including tRNATyr from the L-strand transcripts and tRNAAsp from the H-strand transcripts. Strikingly, mutant cybrids exhibited the lower level of COX2 mRNA and accumulation of longer and uncleaved precursors of COX2 from the H-strand transcripts. Aberrant RNA metabolisms yielded variable reductions in the mitochondrial proteins, especially marked reductions in the levels of ND4, ND5, CO1, CO2 and CO3. The impairment of mitochondrial translation caused the proteostasis stress and respiratory deficiency, diminished ATP production and membrane potential, increased production of reactive oxygen species and promoted apoptosis. Our findings provide new insights into the pathophysiology of deafness arising from mitochondrial tRNA processing defects.

In vitro Development of Preimplantation Caprine Embryo using Cryopreserved Black Bengal Buck Semen

The aim of the present study was to produce goat embryo in different culture media through in vitro fertilization using cryopreserved black Bengal buck semen. Total 1265 fresh cumulus oocyte complexes (COCs) were collected by aspiration method with a 19 gauge hypodermic needle, washed 5-6 times and cultured in maturation media maintaining 5% CO2 level at 38.5ºC with maximum humidity in a incubator. After 27 h of incubation cumulus cells were stripped off from matured oocytes and transferred to acidified Tyrode’s medium for zona thinning and co-incubated with in vitro capacitated sperms for fertilization in Fert-BO media. In the experiment I, fresh buck semen and in experiment II, frozen buck semen was used for in vitro fertilization after in vitro processing. After 5 h of co-incubation, presumptive zygotes were washed and co-incubated with oviductal cells in three different culture media (RVCL, mSOF, KSOM) for further development. In fresh group cleavage (%) were 37.76 ± 2.98, 39.60 ± 1.75, 29.01 ± 1.74, and morula formation (%) were 7.72 ± 3.38, 6.03 ± 1.29, and 3.00 ± 3.00 in RVCL, mSOF and KSOM media respectively. However, in frozen group cleavage (%) were 29.17 ± 2.56, 27.70 ± 2.31, 24.17 ± 1.44 in RVCL, mSOF and KSOM media respectively and morula formation (%) was 2.93 ± 0.97 only in RVCL media. These results indicate that cryopreserved black Bengal buck semen have competence to produce embryos and could be used for embryo development in RVCL media through in vitro fertilization.

Composition and processing activity of a semi-recombinant holo U7 snRNP

In animal cells, replication-dependent histone pre-mRNAs are cleaved at the 3′ end by U7 snRNP consisting of two core components: a ∼60-nucleotide U7 snRNA and a ring of seven proteins, with Lsm10 and Lsm11 replacing the spliceosomal SmD1 and SmD2. Lsm11 interacts with FLASH and together they recruit the endonuclease CPSF73 and other polyadenylation factors, forming catalytically active holo U7 snRNP. Here, we assembled core U7 snRNP bound to FLASH from recombinant components and analyzed its appearance by electron microscopy and ability to support histone pre-mRNA processing in the presence of polyadenylation factors from nuclear extracts. We demonstrate that semi-recombinant holo U7 snRNP reconstituted in this manner has the same composition and functional properties as endogenous U7 snRNP, and accurately cleaves histone pre-mRNAs in a reconstituted in vitro processing reaction. We also demonstrate that the U7-specific Sm ring assembles efficiently in vitro on a spliceosomal Sm site but the engineered U7 snRNP is functionally impaired. This approach offers a unique opportunity to study the importance of various regions in the Sm proteins and U7 snRNA in 3′ end processing of histone pre-mRNAs.

Pretreatment of Refractory Gold Ores Using Cell-Free Extracts of P. chrysosporium: A Preliminary Study

The fungus Phanerochaete chrysosporium has been proven to biotransform refractory gold ores, leading to increase in gold recovery. This transformation has been attributed to enzymes secreted by the microbe. This paper reports the findings of preliminary investigations aimed at assessing the use of hydrogen peroxide and cell-free extracts from the fungus, P. chrysosporium, to effect biotransformation of sulphidic refractory gold ores. The investigations show that the total dissolved arsenic, iron and sulphur in solution were up to 5.2 wt%, 0.9 wt% and 6.0 wt% respectively from flotation concentrate after 72 hrs of treatment. Analysis for sulphide sulphur in the residual solids of the gold concentrate indicated about 25 wt% oxidation within 24 hours of treatment. In general, cell-free decomposition of the samples did not increase beyond 24 hours of contact time, possibly due to exhaustion of the active components. Gold extraction by cyanidation increased by 24% after 24-hr treatment with the cell-free extracts. Comparatively, cell-free (in vitro) treatment recorded 66% overall gold recovery as against 61% for whole cell (in vivo) after 72 hours of treatment. These initial results indicate clearly that in vitro processing is a promising alternative to in vivo processing of refractory gold ores using P. chrysosporium.