Activation of Yeast Mitochondrial Translation: Who Is in Charge?

Mitochondrial genome has undergone significant reduction in a course of evolution; however, it still contains a set of protein-encoding genes and requires translational machinery for their expression. Mitochondrial translation is of the prokaryotic type with several remarkable differences. This review is dedicated to one of the most puzzling features of mitochondrial protein synthesis, namely, the system of translational activators, i.e., proteins that specifically regulate translation of individual mitochondrial mRNAs and couple protein biosynthesis with the assembly of mitochondrial respiratory chain complexes. The review does not claim to be a comprehensive analysis of all published data; it is rather focused on the idea of the "core component" of the translational activator system.

Binding of DNA with Abf2p Increases Efficiency of DNA Uptake by Isolated Mitochondria.

Mutations in mitochondrial DNA often lead to severe hereditary diseases that are virtually resistant to symptomatic treatment. During the recent decades, many efforts were made to develop gene therapy approaches for treatment of such diseases using nucleic acid delivery into the organelles. The possibility of DNA import into mitochondria has been shown, but this process has low efficiency. In the present work, we demonstrate that the efficiency of DNA import can be significantly increased by preforming its complex with a mitochondria-targeted protein nonspecifically binding with DNA. As a model protein, we used the yeast protein Abf2p. In addition, we measured the length of the DNA site for binding this protein and the dissociation constant of the corresponding DNA-protein complex. Our data can serve as a basis for development of novel, highly efficient approaches for suppressing mutations in the mitochondrial genome.

Mitochondrial Fission and Fusion.

Mitochondria are key cellular organelles responsible for many different functions. The molecular biology of mitochondria is continuously subject to comprehensive studies. However, detailed mechanisms of mitochondrial biogenesis are still unclear. Fusion and fission are among the most enigmatic processes connected with mitochondria. On the other hand, it has been shown that these events are of great biological importance for functioning of living cells. In this review, we summarize existing molecular data on mitochondrial dynamics and discuss possible biological functions of fusion and fission of these organelles.

Protein biosynthesis in mitochondria.

Translation, that is biosynthesis of polypeptides in accordance with information encoded in the genome, is one of the most important processes in the living cell, and it has been in the spotlight of international research for many years. The mechanisms of protein biosynthesis in bacteria and in the eukaryotic cytoplasm are now understood in great detail. However, significantly less is known about translation in eukaryotic mitochondria, which is characterized by a number of unusual features. In this review, we summarize current knowledge about mitochondrial translation in different organisms while paying special attention to the aspects of this process that differ from cytoplasmic protein biosynthesis.

[Current features of HIV-infection in St. Petersburg].

Dynamics of HIV-infection epidemic in St. Petersburg was analyzed. New features of epidemic process, which were not observed in St. Petersburg earlier, whereas noted in other territories of Russia, were revealed and described.

[Directed import of macromolecules into mitochondria].

Mitochondria are multifunctional organelles of eukaryotic cells that provide the energy for the cells by oxidative phosphorylation, play an important role in the apoptosis and take part in Fe-S clusters formation, fatty acids oxidation and synthesis of some aminoacids. They contain their own genome and are able to transcribe and to translate it. However, the vast majority of the macromolecules which function inside the mitochondria are imported into these organelles from the cytoplasm. The imported macromolecules include proteins and several types of small RNAs. Protein import is a universal process and its mechanism is conserved among all species. This mechanism is now known in detail. RNA import was shown to occur in several groups of eukaryotes, while the pool of imported RNA molecules varies in different organisms. Although the knowledge about the mechanisms of RNA import is less extensive than for the proteins, it becomes clear that these mechanisms are not universal among all the species possessing this pathway. In this review, we summarize the data about the import of macromolecules mentioned above into mitochondria.

[Analysis of death rates in patients with tuberculosis and HIV infection].

The proportion of those who died at a hospital in 2001 is 3.8% of the treated patients and that in 2002 is 4.2%. In 2003, mortality rates increased more than 3-fold and accounted for 13.4%. Patients with a long history of tuberculosis were found to have pulmonary tuberculosis without extrapulmonary foci. Generalized forms of tuberculosis were detectable in more than a third of the cases and more frequently encountered in patients with significant immunodeficiency for whom tuberculosis was opportunistic infection.

[Isolation and cloning of gene for hepatitis delta antigen. The use of recombinant antigen for serodiagnosis of delta infection]. / Vydelenie i klonirovanie gena antigena virusa gepatita del'ta. Ispol'zovanie rekombinantnogo antigena dlia serodiagnostiki del'ta-infektsii.

Hepatitis delta virus antigen was isolated from a patient by reverse transcription and polymerase chain reaction. Gel-purified cDNA was cloned in E. coli expression vectors. High expression of the recombinant HDAg in bacteria was observed. The minor and major forms of HDV antigens were simultaneously expressed in bacterial strains carrying SupE mutation. A laboratory method is developed for detecting anti-HD in patients' blood. It is based on the use of minor and major forms of recombinant HDV antigen immobilized on the same membrane filter. The method can be used for creating an original highly specific test system.

[The frequency of antibodies against delta virus in patients with HBs positive hepatitis]. / Chastota antitel k del'ta-virusu u bol'nykh HBs-pozitivnym gepatitom.

Patients with HBsAg-positive hepatitis were screened for antibodies to HDV and HCV. The incidence of anti-HDV was 12.5% in a sample of 265 patients. The values differed appreciably in men and women, patients with chronic and acute hepatitis, narcomaniacs and subjects taking no narcotics. Antibodies to HDV were more incident in anti-HCV-positive than in anti-HCV-negative patients. The age-specific structure of the sampling has been analyzed and the distribution of HDV, HCV, narcomania, and chronic hepatitis markers for age groups has been determined. A high incidence of mixed (double and triple) infections with hepatotropic viruses has been revealed.

[Usage of polymerase chain reaction in complex diagnosis of hepatitis B]. / Primenenie polimeraznoi tsepnoi reaktsii v kompleksnoi diagnostiki gepatita B.

Sera from 926 patients were analyzed by PCR using universal primers to surface gene of hepatitis B virus (HBV). HBV DNA was detected in 195 specimens. There were no serological markers of HBV in 8.2% of these sera, but later they were detected in patients' sera. In patients without HBV DNA in the serum, specific HBV antigens and antibodies were detected in 62%. Only in 14% of them the clinical picture of the disease corresponded to acute viral hepatitis, although the blood for PCR analysis was collected during the late stages of the infection. The rest cases were referred to mixed hepatitis C + D. Comparison of the results of PCR test and detection of serological virus replication markers HBeAg and HBeAb showed the presence of HBV DNA in 28% cases without HBeAg.

[Viral hepatitis A: causes of lingering]. / O nekotorykh prichinakh zatiazhnykh form virusnogo gepatita A.

The examination covered 756 patients with viral hepatitis A (90 of them were followed up for 1.5 years) who had antigens and antibodies to hepatitis A, B, C, E and D viruses. It was found that: lingering viral hepatitis A may be caused by viral persistence marked by specific antibodies (IgM anti-HAV); lingering hepatitis followed by verification of chronic hepatitis is related to manifestation of previous hepatitis B and C; detection of IgM anti-HAV in patients with exacerbation of chronic hepatitis B, C and D (hepatitis D) evidences for the presence of mix-infection (acute hepatitis A in chronic hepatitis B, C or D).

[Protracted forms of viral hepatitis A in adolescents]. / Zatiazhnye formy virusnogo gepatita A u podrostkov.

The results of study of the clinical picture and outcomes of type A viral hepatitis (HA) in 80 male adolescents aged 15-18 years are presented. The diagnosis was confirmed serologically. A greater incidence of the protracted forms of HA has been found in adolescents which in most cases had a favourable outcome. Protracted hepatitis was marked by long-term persistence of anti-HVA IgM. The chronic form of viral hepatitis had a course of a mixed A and B viral infection.

[Use of regional lymphotropic therapy in the treatment of pulmonary tuberculosis in HIV-infected individuals]. / Primenenie regionarnoi limfotropnoi terapii v lechenii tuberkuleza legkikh u VICH-infitsirovannykh lits.

The efficiency of regional lymphotropic therapy (RLT) used to treat tuberculosis in HIV-infected patients was analyzed. With this treatment, the symptoms of intoxication are eliminated more rapidly. In shorter periods, bacterial isolation ceases and decay cavities close in the majority of patients. This chemotherapy is better tolerated and toxic reactions occur less frequently. Due to its absolute controllability, RLT is may be used in socially dysadapted patients.

[The comparative characteristics of test systems for the diagnosis of viral hepatitis D]. / Sravnitel'naia kharakteristika test-sistem dlia diagnostiki virusnogo gepatita D.

Three Russian enzyme immunoassay kits for the detection of antibodies to hepatitis D virus (delta virus) in the blood serum were compared. Labsystems test kit was the control. Two of the examined kits were found sufficiently sensitive and specific, comparable with those of the imported agent.