Pulmonary Mycobacterium Simiae infection and HTLV1 infection: an incidental co-infection or a predisposing factor?

There is little information on atypical mycobacterium and human T lymphothropic virus Type I (HTLV-I) co-infection. We present the first case of pulmonary M. simiae infection in co-infection with HTLV-1, confirmed by ELISA antibody test and Western Blot. We discuss the clinical characteristics and laboratory tests of the patient and presumptive immunological relation. We propose that in patients with the HTLV infection and pulmonary symptoms and signs compatible with tuberculosis, evaluation for atypical mycobacteriosis may be recommendable

Subnucleosome particles containing high mobility group proteins HMG-E and HMG-G originate from transcriptionally active chromatin.

Subnucleosome particles SN2 and SN3 containing short DNA fragments and non-histone proteins of the high mobility group, HMG-G and HMG-E respectively, were purified from the chromatin preparations of mouse L cells partially digested with staphylococcal nuclease. Labeled DNAs prepared from these particles were hybridized to an excess of nuclear RNA. The binding of subnucleosomal DNA was about 3-fold higher comparing to total cellular DNA fragmented to the same size. Special control experiments showed that DNA.protein complexes present in subnucleosomes SN2 and SN3 preexisted in nontreated nuclei. The conclusion has been drawn that non-histone proteins HMG-G and HMG-E are associated with the DNA of transcriptionally active chromatin and are released by nuclease as subnucleosomes

Heterogeneity of chromatin subunits in vitro and location of histone H1.

Chromatin subunits ("nucleosomes") which were purified by sucrose gradient centrifugation of a staphylococcal nuclease digest of chromatin have been studied. We found that such a preparation contains nucleosomes of two discrete types which can be separated from each other by polyacrylamide gel electrophoresis. Nucleosome of the first type contains all five histones and a DNA segment of approximately 200 base pairs long, whereas nucleosome of the second type lacks histone H1 and its DNA segment is approximately 170 base pairs long, i.e., about 30 base pairs shorter than the DNA segment of the nucleosome of the first type. Purified dimer of the nucleosome also can be fractionated by gel electrophoresis into three discrete bands which correspond to dinucleosomes containing two molecules of histone H1, one and no H1. These and related findings strongly suggest that the H1 molecule is bound to a short (approximately 30 base pairs) terminal stretch of the nucleosomal DNA segment which can be removed by nuclease (possibly in the form of H1-DNA complex) without any significant disturbance of main structural features of the nucleosome

Effect of X-ray induced DNA damage on DNAase I hypersensitivity of SV40 chromatin: relation to elastic torsional strain in DNA.

The effect of X-irradiation on DNAase I hypersensitivity of SV40 minichromosomes within nuclei or free in solution was investigated. The susceptibility of the specific DNA sites in the control region of minichromosomes to DNAase I decreased in a dose dependent manner after irradiation of isolated nuclei. On the other hand, the irradiation of minichromosomes extracted from nuclei in 0.1 M NaCl-containing buffer almost did not affect the level of their hypersensitivity to DNAase I. This suggests that DNAase I hypersensitivity may be determined by two different mechanisms. One of them may be connected with elastic torsional strain within a fraction of minichromosomes and another seems to be determined by nucleosome free region. The first mechanism may be primarily responsible for the hypersensitivity of minichromosomes within nuclei. After irradiation of the intact cells, DNAase I hypersensitivity tested in nuclei substantially increased. This was connected with activation of endogeneous nucleases by X-irradiation which led to accumulation of single- and double-strand breaks superimposed to DNAase I induced breaks in the control region of SV40 DNA

Nucleosomes and subnucleosomes: heterogeneity and composition

Previous studies (Varshavsky, Bakayev and Georgiev, 1976a) have shown that chromatin subunits (mononucleosomes) and their oligomers in a mild staphylococcal nuclease digest of chromatin display a heterogeneous content of histone H1. We now report that a mild staphylococcal nuclease digest of either chromatin or nuclei from mouse Ehrlich tumor cells contains mononucleosomes of three discrete kinds. The smallest mononucleosome (MN₁) contains all histones except H1 and a DNA fragment 140 base pairs (bp) long. The intermediate mononucleosome (MN₂) contains all five histones and a DNA fragment 170 bp long. The third mononucleosome (MN₃) also contains all five histones, but its DNA fragment is longer and more heterogeneous in size (180–200 bp). Most of the MN₃ particles are rapidly converted by nuclease into mononucleosomes MN₁ and MN₂. There exists, however, a relatively nuclease-resistant subpopulation of the MN₃ mononucleosomes. These 200 bp MN₁ particles contain not only histones but also nonhistone proteins, and are significantly more resistant to nuclease than the bulk of MN₃ particles and the smaller mononucleosomes MN₁ and MN₂. There are eight major kinds of staphylococcal nuclease-produced soluble subnucleosomes (SN). The SN₁ is a set of naked double-stranded DNA fragments ∼20 bp long. The SN₂ is a complex of a specific basic nonhistone protein (molecular weight ∼16,000 daltons) and a DNA fragment ∼27 bp long. The SN₃ contains histone H4, the above-mentioned specific nonhistone protein and a DNA fragment ∼27 bp long. The SN4 contains histones H2a, H2b, H4 and a DNA fragment ∼45 bp long. The SN5 contains histones H2a, H2b, H3 and a DNA fragment ∼55 bp long. The SN6 is a complex of histone H1 and a DNA fragment ∼35 bp long. Subnucleosomes SN₇ and SN₈ each contain all the histones except H1, and DNA fragments ∼100 and ∼120 bp long, respectively. Nuclease digestion of isolated mono- or dinucleosomes does not produce some of the subnucleosomes. These and related findings indicate that the cleavage required to generate these subnucleosomes result from some aspect of chromatin structure which is lost upon digestion to mono- and dinucleosomes