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At least 73 records · Page 4Linked to original sources
PubMed1987

An H1-like protein from the macronucleus of Euplotes eurystomus.

An H1-like protein has been purified from the macronucleus (MAC) of the hypotrichous ciliated protozoan, Euplotes eurystomus. It is present in amounts comparable to the inner histones and is extracted by treatment with 5% perchloric acid or 0.65 M NaCl, but not by 0.35 M NaCl. Treatment of soluble MAC chromatin with the ionic exchange resin AG 50W-X2 in 80 mM NaCl removes MAC H1 and yields H1-depleted chromatin. Mac H1 is lysine-rich and deficient in acidic amino acids. The stoichiometry of the H1 protein is reduced in mononucleosome preparations, consistent with its postulated interaction with linker DNA regions. Thermal denaturation and circular dichroism studies reveal that H1-depleted chromatin contains a larger portion of destabilized DNA than control chromatin. The molecular weight of Euplotes MAC H1 is significantly smaller than most reported H1 proteins. Comparisons are made with extracts of macronuclei from other hypotrichous ciliated protozoa and published reports of other lower eukaryotes.

Amino Acids↗
PubMedDate not supplied

[Structure of the interphase chromatin in Bursaria truncatella macronucleus. I. Electron microscopic and autoradiographic study of the structural chromatin changes during differentiation and growth after division].

The structure of interphase chromatin from isolated individual macronuclei of Bursaria truncatella was studied at different moments after cell division. During the period 0,5-3 hours after division most of the macronuclear chromatin is represented by loose agglomerations of decondensed chromatin, where transcription complexes can be seen. The maximum quantity of decondensed chromatin is observed 0,5-1,5 hours after cell division. During the period 1,5-3 hours after the division the part of decondensed chromatin decreases along with the increase of the quantity of dense chromatin organized in chromatin clumps 0,12-0,18 mu in diameter. In completely developed vegetative cells nearly all the chromatin has the structure of closely packed chromatin clumps. Electronmicroscopic autoradiography data show that chromatin clumps are transcriptionally inert, whereas all the transcription processes take place in decondensed chromatin agglomerations. The structure of transcription complexes of B. truncatella macronucleus is discussed in detail.

Animals↗
PubMedDate not supplied

[Structure of the interphase chromatin in the ciliata Bursaria truncatella macronucleus. II. Loop organization of inactive chromatin clumps].

Electron microscopic study of chromatin organization in isolated macronuclei of a ciliate Bursaria truncatella showed macronuclear chromatin to be organized in compact clumps 120--180 nm in diameter linked with each other by one or several chromatin fibres. Macronucleus being dispersed in a solution of low ionic strength, radial loops basically of nucleosomal structure start appearing around chromatin clumps. Long-time dispersing of macronuclear chromatin brings complete decompactization of chromatin clumps into a set of nucleosome fibres. The way the fibres of interphase chromatin are packed in a chromatin clump is discussed.

Cell Nucleus↗
PubMedDate not supplied

[Distribution of repeating nucleotide sequences in the macronucleus DNA of Tetrahymena infusoria].

The genome of Tetrahymena pyriformis macronucleus contain less than 10% of repetitive sequences. About half of them consist of long, more than 2000 base pairs, moderately repeated sequences. Short repetitive sequences (200--300 base pairs) represent 4--5% of the genome. We assume, that the short repetitive sequences are interspersed with single copy sequences of about 1000 base pairs. In this case less than 15% of the Tetrahymena DNA should consist of interspersed repetitive and single copy sequences.

Base Sequence↗
PubMed1956

Further observations on the fine structure of the macronucleus in Tokophrya infusionum.

In a previous paper (8) an organized structure was described in the macronuclei of certain old organisms of Tokophrya infusionum. It was found that the same honeycomb structure appears in great abundance in the macronuclei of overfed organisms. This permitted a better three-dimensional reconstruction of the described structure. Since the defined structure may be experimentally induced, it offers an opportunity for further more detailed studies as to its nature and meaning.

Animals↗