Sequences required for paramutation of the maize b gene map to a region containing the promoter and upstream sequences.

The b gene encodes a transcriptional regulator of the maize anthocyanin biosynthetic pathway. Certain b alleles participate in paramutation, an allele-specific interaction that heritably alters transcription. The moderately transcribed B' allele heritably reduces the transcription of the highly transcribed B-I allele in a B'/B-I heterozygote, such that the B-I allele becomes B'. To identify the cis-acting sequences required for paramutation, we used B' or B-I alleles to isolate intragenic recombinants with B-Peru, an allele that is insensitive to paramutation and has distinct tissue-specific regulation. Physical mapping of the recombinant alleles showed that most of the crossovers were in a small region near the 5' end of the b-transcribed region. Analysis of the recombinant alleles revealed that the ability to cause and respond to paramutation and the control of tissue-specific expression both localize to the 5' region of the gene. The 3' boundary of these functions lies just upstream of the translation initiation codon. The 5' boundary has been estimated to be no more than 0.1 cM further upstream (1-150 kb). Thus, sequences critical for paramutation lie upstream of the b coding sequences and may include transcriptional regulatory sequences.

[Contribution to nursing care for patients with mitral valve disease]. / Subsídios para a assistência de enfermagem a pacientes com valvopatia mitral.

The purpose of this study was to define: the profile of patients with mitral valve dysfunction (stenosis and/or insufficiency) who were assisted at the University Outpatients' Clinic, the knowledge that these patients had concerning their disorder and the main difficulties and limitations resulting from it. The necessary data were obtained by interviewing 29 patients from November 1997 to February 1998. An analysis was conducted through the Content Analysis Technique. The results obtained helped to understand the problem under the individual's and his family's viewpoint, which helped to elaborate a nursing care program with an educational focus.

[Ambulatory nursing care for patients with aortic valve disease]. / Levantamento de subsídios para assistência de enfermagem ambulatorial a pacientes portadores de valvopatia aórtica.

This study aimed at characterizing the profile of outpatients with aortic valve dysfunction, identifying their knowledge about the disease, their major limitations during everyday activities and their means of coping with their predicament. The data obtained by semi-structured interviews with 12 patients and analyzed by quantitative and qualitative methods enabled to identify how the patients perceive the illness and the treatment as well as the implications to their everyday activities, that is, they allowed to capture reality from the subject's perspective, which is the knowledge for the elaboration of an educational proposal.

Bacterial transposon Tn7 utilizes two different classes of target sites.

Sites of transposon Tn7 insertion in the Escherichia coli chromosome were examined, and two distinct classes of target sites differing in nucleotide sequence were identified. The target site choice was found to be determined by Tn7-encoded transposition genes.

Tn7 transposition: target DNA recognition is mediated by multiple Tn7-encoded proteins in a purified in vitro system.

We have reconstituted the transposition of the bacterial transposon Tn7 into its specific insertion site attTn7 with four purified Tn7-encoded proteins, TnsA+TnsB+TnsC+TnsD, and ATP. TnsA+TnsB+TnsC form a "core" recombination machine that recognizes the transposon ends and executes DNA breakage and joining; TnsD specifically recognizes attTn7. TnsA+TnsB+TnsC are specifically targeted to attTn7 through the TnsD-dependent interaction of TnsC, a nonspecific DNA-binding protein, with attTn7. Recombination appears to be activated by the assembly of a nucleoprotein complex containing the DNA substrates and Tns proteins. We suggest that TnsC plays a central role in communication between the transposon and the target DNA, particularly in directing insertion away from DNAs already containing a copy of Tn7.

mediator of paramutation1 is required for establishment and maintenance of paramutation at multiple maize loci.

Paramutation is the directed, heritable alteration of the expression of one allele when heterozygous with another allele. Here, the isolation and characterization of a mutation affecting paramutation, mediator of paramutation1-1 (mop1-1), are described. Experiments demonstrate that the wild-type gene Mop1 is required for establishment and maintenance of the paramutant state. The mop1-1 mutation affects paramutation at the multiple loci tested but has no effect on alleles that do not participate in paramutation. The mutation does not alter the amounts of actin and ubiquitin transcripts, which suggests that the mop1 gene does not encode a global repressor. Maize plants homozygous for mop1-1 can have pleiotropic developmental defects, suggesting that mop1-1 may affect more genes than just the known paramutant ones. The mop1-1 mutation does not alter the extent of DNA methylation in rDNA and centromeric repeats. The observation that mop1 affects paramutation at multiple loci, despite major differences between these loci in their gene structure, correlations with DNA methylation, and stability of the paramutant state, suggests that a common mechanism underlies paramutation. A protein-based epigenetic model for paramutation is discussed.