Biomedical subjects

F Forti

Publications and source records attributed to F Forti.

At least 19 recordsLinked to original sources

PubMed2006

Expression of phage P4 integrase is regulated negatively by both Int and Vis.

Phage P4 int gene encodes the integrase responsible for phage integration into and excision from the Escherichia coli chromosome. Here, the data showing that P4 int expression is regulated in a complex manner at different levels are presented. First of all, the Pint promoter is regulated negatively by both Int and Vis, the P4 excisionase. The N-terminal portion of Int appears to be sufficient for such a negative autoregulation, suggesting that the Int N terminus is implicated in DNA binding. Second, full-length transcripts covering the entire int gene could be detected only upon P4 infection, whereas in P4 lysogens only short 5'-end covering transcripts were detectable. On the other hand, transcripts covering the 5'-end of int were also very abundant upon infection. It thus appears that premature transcription termination and/or mRNA degradation play a role in Int-negative regulation both on the basal prophage transcription and upon infection. Finally, comparison between Pint-lacZ transcriptional and translational fusions suggests that Vis regulates Int expression post-transcriptionally. The findings that Vis is also an RNA-binding protein and that Int may be translated from two different start codons have implications on possible regulation models of Int expression.

Artificial Gene Fusion↗

PubMed2006

Proposal for electrical insulation of the electromyographic signal acquisition module.

The aim was to analyze the inteiference in a signal acquisition module (SAM) EMG1000 (Lynx--10(9) Ohms, 16 bits and range of +/-1 V), with active surface electrode (Lynx--gain 20, IRMC > 100 dB) placed over the belly of the brachial biceps of 18 healthy, sedentary volunteers, without osteomyoarticular pathologies in the upper members. Initially, the intrinsic noise of the SAM was assessed by means of a short-circuit between the simple differential and the reference electrodes, and a second stage consisted of collecting the electromyographic signal at rest of the brachial biceps muscle in 4 different procedures. (1) SAM and desktop in the electrical network (EN); (2) SAM in the battery and desktop in the EN; (3) SAM in the EN and desktop connected to the fibre optic (FO) and (4) SAM in the battery and desktop in the FO. The rest signal was collected for 10 seconds and repeated 3 times. RMS and median frequency were assessed with the software Matlab. Under conditions 1, 2 and 3 there was great interference in the signal by EN. Whereas under condition 4, the interference was eliminated. According to the results, the electrical insulation proposed was efficient in eliminating the noise, guaranteeing the quality of the acquired signal.

Adult↗

PubMed2001

The plasmid status of satellite bacteriophage P4.

P4 is a natural phasmid (phage-plasmid) that exploits different modes of propagation in its host Escherichia coli. Extracellularly, P4 is a virion, with a tailed icosahedral head, which encapsidates the 11.6-kb-long double-stranded DNA genome. After infection of the E. coli host, P4 DNA can integrate into the bacterial chromosome and be maintained in a repressed state (lysogeny). Alternatively, P4 can replicate as a free DNA molecule; this leads to either the lytic cycle or the plasmid state, depending on the presence or absence of the genome of a helper phage P2 in the E. coli host. As a phage, P4 is thus a satellite of P2 phage, depending on the helper genes for all the morphogenetic functions, whereas for all its episomal functions (integration and immunity, multicopy plasmid replication) P4 is completely autonomous from the helper. Replication of P4 DNA depends on its alpha protein, a multifunctional polypeptide that exhibits primase and helicase activity and binds specifically the P4 origin. Replication starts from a unique point, ori1, and proceeds bidirectionally in a straight theta-type mode. P4 negatively regulates the plasmid copy number at several levels. An unusual mechanism of copy number control is based on protein-protein interaction: the P4-encoded Cnr protein interacts with the alpha gene product, inhibiting its replication potential. Furthermore, expression of the replication genes cnr and alpha is regulated in a complex way that involves modulation of promoter activity by positive and negative factors and multiple mechanisms of transcription elongation-termination control. Thus, the relatively small P4 genome encodes mostly regulatory functions, required for its propagation both as an episomal element and as a temperate satellite phage. Plasmids that, like P4, propagate horizontally via a specific transduction mechanism have also been found in the Archaea. The presence of P4-like prophages or cryptic prophages often associated with accessory bacterial functions attests to the contribution of satellite phages to bacterial evolution.

Bacteriophage T4↗

PubMed2001

Transcriptional regulation of furA and katG upon oxidative stress in Mycobacterium smegmatis.

The DNA region upstream of katG in Mycobacterium smegmatis was cloned and sequenced. The furA gene, highly homologous to Mycobacterium tuberculosis furA, mapped in this region. The furA-katG organization appears to be conserved among several mycobacteria. The transcription pattern of furA and katG in M. smegmatis upon oxidative stress was analyzed by Northern blotting and primer extension. Although transcription of both furA and katG was induced upon oxidative stress, transcripts covering both genes could not be identified either by Northern blotting or by reverse transcriptase PCR. Specific transcripts and 5' ends were identified for furA and katG, respectively. By cloning M. smegmatis and M. tuberculosis DNA regions upstream of a reporter gene, we demonstrated the presence of two promoters, pfurA, located immediately upstream of the furA gene, and pkatG, located within the terminal part of the furA coding sequence. Transcription from pfurA was induced upon oxidative stress. A 23-bp sequence overlapping the pfurA -35 region is highly conserved among mycobacteria and streptomycetes and might be involved in controlling pfurA activity. Transcription from a cloned pkatG, lacking the upstream pfurA region, was not induced upon oxidative stress, suggesting a cis-acting regulatory role of this region.

Bacterial Proteins↗

PubMed1999

Translation of two nested genes in bacteriophage P4 controls immunity-specific transcription termination.

In phage P4, transcription of the left operon may occur from both the constitutive PLE promoter and the regulated PLL promoter, about 400 nucleotides upstream of PLE. A strong Rho-dependent termination site, timm, is located downstream of both promoters. When P4 immunity is expressed, transcription starting at PLE is efficiently terminated at timm, whereas transcription from PLL is immunity insensitive and reads through timm. We report the identification of two nested genes, kil and eta, located in the P4 left operon. The P4 kil gene, which encodes a 65-amino-acid polypeptide, is the first translated gene downstream of the PLE promoter, and its expression is controlled by P4 immunity. Overexpression of kil causes cell killing. This gene is the terminal part of a longer open reading frame, eta, which begins upstream of PLE. The eta gene is expressed when transcription starts from the PLL promoter. Three likely start codons predict a size between 197 and 199 amino acids for the Eta gene product. Both kil and eta overlap the timm site. By cloning kil upstream of a tRNA reporter gene, we demonstrated that translation of the kil region prevents premature transcription termination at timm. This suggests that P4 immunity might negatively control kil translation, thus enabling transcription termination at timm. Transcription starting from PL proceeds through timm. Mutations that create nonsense codons in eta caused premature termination of transcription starting from PLL. Suppression of the nonsense mutation restored transcription readthrough at timm. Thus, termination of transcription from PLL is prevented by translation of eta.

Amino Acid Sequence↗

PubMed1997

Expression of the SMN gene, the spinal muscular atrophy determining gene, in the mammalian central nervous system.

The survival motor neuron (SMN) gene is the putative disease gene for human spinal muscular atrophy (SMA), an autosomal recessive disorder characterized by progressive degeneration of lower motor neurons. Two copies of the gene, centromeric and telomeric, are present in the same 5q13 chromosomal region in humans. However, only the telomeric gene is affected in SMA. The SMN gene(s) encode(s) a novel protein of unknown function. To gain insights into the role of SMN in neurons, we have identified the SMN gene ortholog in the rat, and investigated SMN expression in the CNS of rat, monkey and humans by immunocytochemistry and in situ hybridization experiments. Antibodies against the SMN amino-terminus specifically recognized a single protein identical to the in vitro translation products of human and rat SMN cDNAs. The SMN gene transcript and product were widely but unevenly expressed throughout cerebral and spinal cord areas. The SMN protein was localized mainly in the cytoplasm of specific neuronal systems, and it was particularly expressed in lower motor neurons of newborn and adult animals. Likewise, a strong hybridization signal was detected in lamina IX of the spinal ventral horn. These results support the relevance of SMN for the motor neuron function and the pathogenetic role of the SMN gene in the neuronal degeneration associated with SMA.

Amino Acid Sequence↗

PubMed1997

Identification of the gene encoding the human mitochondrial RNA polymerase (h-mtRPOL) by cyberscreening of the Expressed Sequence Tags database.

A gene cloning strategy based on the screening of the Expressed Sequence Tags database (dbEST) using sequences of mitochondrial housekeeping proteins of yeast was employed to identify the cDNA encoding the precursor of the human mitochondrial RNA polymerase (h-mtRPOL). The 3831 bp h-mtRPOL cDNA is located on chromosome 19p13.3 and encodes a protein of 1230 amino acid residues. The protein sequence shows significant homologies with sequences corresponding to mitochondrial RNA polymerases from lower eukaryotes, and to RNA polymerases from several bacteriophages. The mitochondrial RNA polymerase carries out the central activity of mitochondrial gene expression and, by providing the RNA primers for replication-initiation, is also implicated in the maintenance and propagation of the mitochondrial genome. Genes involved in the control of mtDNA replication and gene expression are attractive candidates for human disorders due to abnormalities of nucleo-mitochondrial intergenomic signalling. The availability of the h-mtRPOL cDNA will allow us to test its role in mitochondrial pathology. In addition, we propose the 'cyberscreening' of dbEST, based on yeast/human cross-species comparison, as a powerful, simple, rapid and inexpensive method, that may accelerate several-fold the molecular dissection of the human mitochondrial proteome.

Amino Acid Sequence↗

PubMed1995

Immunity determinant of phage-plasmid P4 is a short processed RNA.

In the phage-plasmid P4, both lysogenic and lytic functions are coded by the same operon. Early after infection the whole operon is transcribed from the constitutive promoter PLE. In the lysogenic condition transcription from PLE terminates prematurely and only the immunity functions, which are proximal to the promoter, are thus expressed. Fragments of the P4 immunity region were cloned in an expression vector. A DNA fragment as short as 91 bp was sufficient, when transcribed, to express P4 immunity and to complement P4 immunity deficient mutants. This fragment, like prophage P4, produced a 69 nt long RNA (CI RNA). A shorter P4 fragment neither expressed immunity nor synthesized the CI RNA. Thus the CI RNA is the P4 trans-acting immunity factor. The 5' end of the CI RNA, mapped by primer extension, does not correspond to the transcription initiation point, thus suggesting that the CI RNA is produced by processing of the primary transcript. In an RNase P mutant host the processing of the 5' end and the production of a functional CI RNA were impaired. The requirement of RNase P for the correct processing of CI appears to be related to the predicted secondary structure of the precursor CI RNA. A region (seqB) within the CI RNA shows complementarity with two cis-acting sequences (seqA and seqC) required for P4 immunity, suggesting that transcription termination may be caused by pairing of the CI RNA with the complementary target sequences on the nascent transcript.

Base Sequence↗

PubMed1995

Multiple regulatory mechanisms controlling phage-plasmid P4 propagation.

Bacteriophage P4 autonomous replication may result in the lytic cycle or in plasmid maintenance, depending, respectively, on the presence or absence of the helper phage P2 genome in the Escherichia coli host cell. Alternatively, P4 may lysogenize the bacterial host and be maintained in an immune-integrated condition. A key step in the choice between the lytic/plasmid vs. the lysogenic condition is the regulation of P4 alpha operon. This operon may be transcribed from two promoters, PLE and PLL, and encodes both immunity (promoter proximal) and replication (promoter distal) functions. PLE is a constitutive promoter and transcription of the downstream replication genes is regulated by transcription termination. The trans-acting immunity factor that controls premature transcription termination is a short RNA encoded in the PLE proximal part of the operon. Expression of the replication functions in the lytic/plasmid condition is achieved by activation of the PLL promoter. Transcription from PLL is insensitive to the termination mechanism that acts on transcription starting from PLE.PLL is also negatively regulated by P4 orf88, the first gene downstream of PLL. An additional control on P4 DNA replication is exerted by the P4 cnr gene product.

Bacteriophage P1↗

PubMed1995

Control of transcription termination by an RNA factor in bacteriophage P4 immunity: identification of the target sites.

Prophage P4 immunity is elicited by a short, 69-nucleotide RNA (CI RNA) coded for within the untranslated leader region of the same operon it controls. CI RNA causes termination of transcription that starts at the promoter PLE and prevents the expression of the distal part of the operon that codes for P4 replication functions (alpha operon). In this work, we identify two sequences in the untranslated leader region of the alpha operon, seqA and seqC, that are the targets of the P4 immunity factor. seqA and seqC exhibit complementarity to a sequence internal to the CI RNA (seqB). Mutations in either seqA or seqC that alter its complementarity to seqB abolished or reduced P4 lysogenization proficiency and delayed the shutoff of the long transcripts originating from PLE that cover the entire operon. Both seqA and seqC single mutants were still sensitive to P4 prophage immunity, whereas P4 seqA seqC double mutants showed a virulent phenotype. Thus, both functional sites are necessary to establish immunity upon infection, whereas a single site appears to be sufficient to prevent lytic gene expression when immunity is established. A mutation in seqB that restored complementarity to both seqA and seqC mutations also restored premature termination of PLE transcripts, thus suggesting an important role for RNA-RNA interactions between seqB and seqA or seqC in P4 immunity.

Base Sequence↗

PubMed1994

[Juvenile hereditary chorea. Study of a family with recessive pattern of transmission].

Report of a family in which the parents are consanguineous and healthy and 4 of their 8 children began with involuntary choreic movements at ages 10 to 14. In all cases the clinical manifestations remained stable throughout the 5-year period of observation. There have been no clinical deterioration and intellectual functions were found to be intact. All patients were submitted to neurologic examination, neuropsychological testing, CT-scan, cerebrospinal fluid analysis, electroencephalogram, serum copper and ceruloplasmin among other blood tests. These cases were diagnosed as having "juvenile hereditary chorea" from the typical clinical manifestations and after exclusion of other known causes of chorea. Relevant clinical aspects and possible differential diagnosis are discussed along with some advancing hypothesis concerning its relationship with other hereditary diseases presenting with chorea.

Adolescent↗

PubMed1992

Genetic analysis of the immunity region of phage-plasmid P4.

In the prophage P4, expression of the early genes is prevented by premature termination of transcription from the constitutive promoter PLE. In order to identify the region coding for the immunity determinant, we cloned several fragments of P4 DNA and tested their ability to confer immunity to P4 superinfection. A 357 bp long fragment (P4 8418-8774) is sufficient to confer immunity to an infecting P4 phage and to complement the immunity-defective P4 cl405 mutant, both in the presence and in the absence of the helper phage P2. The immunity region covers PLE and the cl locus. We were unable to obtain evidence of translation of the region, thus we suggest that P4 immunity is not elicited by a protein but by a transcript (or transcripts) encoded by the region downstream of the promoter PLE. The promoter PLE appears to be necessary for the expression of P4 immunity: fragments in which the PLE region is deleted did not complement P4 cl405 for lysogenization, although they still interfered with P4 growth. Two complementary sequences downstream of PLE (seqA and seqB) at the 5' and 3' ends of the immunity region play an essential role in the control of P4 immunity.

Base Sequence↗

PubMed1991

[Focal crisis induced by movement in a patient with nonketotic hyperglycemia].

Case report of a long term diabetic patient with partial motor crisis originating from passive movement of the right arm. This is a rare type of crisis when compared to spontaneous partial crisis in diabetic patients. Partial crises are often the initial manifestation of diabetes mellitus (about 19% of the cases reported). As in those cases registered in the literature, crisis control in this case was obtained by normalization of glycose serum levels. Possible mechanisms involved in the pathogenesis are discussed.

Aged↗

PubMed1984

[Immediate effects of cerebral gangliosides in peripheral neuropathies: electromyographic evaluation].

The effects of the cerebral cortex gangliosides have been studied in fifteen patients with peripheral neuropathies through the results of electromyographic examination. The patients were divided into two groups: A--peripheral neuropathy of alcoholic etiology (seven patients); D--peripheral neuropathy of diabetes etiology (eight patients). The medication has been administered 20 mg/day intramuscularly during twenty days. At the end of that period it was verified: 1) a discrete increase of the motor conduction velocity in the patients of the group A; 2) the sensitive conduction velocity was inaltered in both groups; 3) a favourable therapeutic response (global evaluation) in three patients of group A, and in three of group D; they represent 40% of the total number of patients studied. For the control of therapeutical effects of the medication the authors suggest a more prolonged period of administration of the medication in hospitalized patients submitted to periodic electromyographic examinations.

Adult↗

PubMed1980