Carlos Morel

Proteins associated with globin messenger RNA in avian erythroblasts: Isolation and comparison with the proteins bound to nuclear messenger-likie RNA.

There is evidence that the polyribosomal messenger RNA (mRNA) in animal cells is specifically associated with proteins [l-7] . In the case of cytoplasmic [5,8] or nuclear [9] messenger-like RNA (mlRNA) similar RNA-protein (RNP) complexes have also been described. Contrary to the claim that such associations may be non-specific [ 10, 1 l] , adequate control experiments suggest that they pre-exist in the cell and are not artefacts produced during lysis [5,8, 121. The exact physiological significance of these structures is not known. They may play a variety of roles such as: protection against RNase attack [5,8], RNA transport [ 1,8,9] , cleavage of giant mlRNA and selection of the RNA molecules to be transferred to the cytoplasm [5,9] , or initiation of protein synthesis [7] . In particular, two reports [ 13, 141 claim that the protein bound to the giant nuclear mlRNA is the same as that associated with mRNA in polyribosomes, indicating a possible function in mRNA transport. We have studied these mRNP particles in a highly differentiated system: duck immature red blood cells. In contrast to the hemoglobin producing cells in mammals, duck red cells are nucleated, making possible the investigation of the mland mRNA complexes in the nucleus and in the cytoplasm of a cell where a specific mRNA can be identified.

Biochemical strain characterization of Trypanosoma cruzi by restriction endonuclease cleavage of kinetoplast-DNA

An important problem in the study of Typanosoma cruzi, the agent of Chagas’ disease, is the characterization of the different strains isolated from patients or vectors. Differences between T. cruzi strains have already been shown in relation to criteria such as antigenic constitution [l], isoenzyme patterns [2], drug sensitivity [3], parasitemia curve in experimentally infected animals [4], proportion of trypomastigotes to epimastigotes in culture [5] and dependence on temperature of intracellular differentiation [6]. These differences suggest the occurrence of subspecies in T. cruzi and demand sensitive methods for routine strain characterization. In this paper we show that restriction endonuclease [7] digestion of isolated kinetoplastDNA provides a powerful tool for the molecular typing of T. cruzi at the genotype level.

EDTA- and puromycin-derived duck- and rabbit globin-messenger ribonucleoprotein complexes isolated by oligo(dT)-cellulose chromatography

Duck- and rabbit globin messenger ribonucleoprotein complexes isolated by oligo(dT) cellulose chromatography reveal an identical protein pattern—two main proteins of molecular weights of 73000 and 49000 daltons and minor components—whether the complexes have been liberated from polyribosomes with the EDTA-or the puromycin-high-salt method. In the globin messenger ribonucleoprotein particles of both species predominantly the protein with a molecular weight of 73000 daltons is attached to poly(A)-containing regions of the messenger RNAs.

Different sensitivities of avian- and mammalian-haemoglobin synthesis to elevated temperatures

Avian- and mammalian-haemoglobin synthesis show different sensitivities to elevated temperatures. Temperature-dependent, reversible polyribosome disaggregation in avian cells occurs only at 45°C, which is 3° higher than the temperature for mammalian cells, and seems to be due to a block in the initiation of new polypeptide chains. The implications of these findings are discussed.