Yeast two-hybrid cloning of a novel zinc finger protein that interacts with the multifunctional transcription factor YY1.

Muscle-restricted transcription of sarcomeric actin genes is negatively controlled by the zinc finger protein YY1, which is down-regulated at the protein level during myogenic differentiation. To identify cellular proteins that might mediate the function/stability of YY1 in muscle cells, we screened an adult human muscle cDNA library using the yeast two-hybrid cloning system. We report the isolation and characterization of a novel protein termed YAF2 (YY1- associated factor 2) that interacts with YY1. The YAF2 cDNA encodes a 180 amino acid basic protein (pI 10.5) containing a single N-terminal C2-X10-C2 zinc finger. Lysine clusters are present that may function as a nuclear localization signal. Domain mapping analysis shows that the first and second zinc fingers of YY1 are targeted for YAF2 protein interaction. In contrast to the down-regulation of YY1, YAF2 message levels increase during in vitro differentiation of both rat skeletal and cardiac muscle cells. YAF2 appears to have a promyogenic regulatory role, since overexpression of YAF2 in C2 myoblasts stimulates myogenic promoter activity normally restricted by YY1. Co-transfection of YY1 reverses the stimulatory effect of YAF2. YAF2 also greatly potentiates proteolytic cleavage of YY1 by the calcium- activated protease m-calpain. The isolation of YAF2 may help in understanding the mechanisms through which inhibitors of myogenic transcription may be antagonized or eliminated by proteolysis during muscle development.

Analysis of events associated with serum deprivation-induced apoptosis in C3H/Sol8 muscle satellite cells.

Satellite cells are the source of new muscle fibers in postnatal skeletal muscle growth and regeneration. Regulation of satellite cell survival is of fundamental importance in maintaining normal muscle function. Here we describe and characterize a tissue culture model of satellite cell apoptosis. Kinetic studies indicate that serum deprivation triggers a set of sequential events: early cell death, transient cell cycle traverse, and delayed cell death. The satellite cell death occurs by apoptosis based on the internucleosomal DNA laddering, in situ DNA end-labeling, and the requirements for de novo protein synthesis and extracellular calcium influx. The transient period of cell cycle progression (7-11 h after serum withdrawal) is accompanied by temporal induction of members of the immediate early gene family, such as c-myc, c-fos, and SRF, and appears to precede the delayed phase of cell death. Satellite cell apoptosis can be suppressed by several growth factors and by blocking the activity of calpain, a calcium-regulated protease. The late phase of apoptosis is marked by selective activation of ubiquitin-mediated protein conjugation and degradation. This study defines several control points where satellite cell apoptosis may be genetically or pharmacologically intervened.

[Role of toxoplasmosis in the development of central nervous system lesions in children]. / Die Rolle der Toxoplasmose für die Entstehung von Schädigungen des Zentralnervensystems bei Kindern.

Because of the high degree of infestation in women capable of bearing children in Europe (70 to 80%) with Toxoplasma gondii the authors have studied all babies admitted for clinical treatment at the institute of Paediatrics in Lublin for clinical and serological indications of a connatal toxoplasmosis. In the period between January 1977 and December 1978, 133 babies showed positive findings. The most frequently occurring findings were lesions of the central nervous system (hydrocephalus 21 X, microcephaly 8 X, porencephaly 18 X, convulsions and psychomotor retardation 11 X, subdural hygroma and haematoma 34 X, encephalomeningitis 7 X). Intracranial calcifications within the classical triad were only found in two cases. Other internal lesions without cerebral deficiency symptoms were found in 18 children. The authors point out the possible connection between vascular lesions caused by toxoplasmosis and subdural effusions. One might think of both permeability disturbances and direct vascular lacerations. The treatment consisted in repeated punctures, trepanations and antibiotics (Spiramycin, Daraprim, Orisul). The serological proof of the presence of toxoplasmosis may well lag behind the clinical symptoms.

[Subdural hygroma in infants with congenital toxoplasmosis (author's transl)]. / Die subduralen Hygrome bei den Säuglingen mit angeborener Toxoplasmose.

Cytological examination of the fluid from subdural hygromas revealed congenital Toxoplasmosis in 14 of 43 infants (32,5%). Conversely, subdural hygroma was a significant clinical symptom in 42 cases of congenital Toxoplasmosis. In 9 cases trophozoites or cystes of Toxoplasma Gondii were found in the subdural fluid, and in 4 of these in the cerebrospinal fluid as well. Since serological investigations in young infants and particularly severe infections often remain inconclusive the cytological examination of cerebrospinal fluid is emphasized importance of.