The MLL/Setd1b methyltransferase is required for the Spemann's organizer gene activation in Xenopus

Chromatin structure at the fundamental level of the nucleosome is important in vital cellular processes. Recent biochemical and genetic analyses show that nucleosome structure and structural changes are very active participants in gene expression, facilitating or inhibiting transcription and reflecting the physiological state of the cell. Structural states and transitions for this macromolecular complex, composed of DNA wound about a heterotypic octamer of variously modified histone proteins, have been measured by physico-chemical techniques and by enzyme-accessibility and are recognized to occur with various post-translational modifications, gene activation, transformation and with ionic-environment. In spite of studies which indicate various forms of nucleosome structure, all current x-ray and neutron diffraction studies have consistently resulted in only one structure, suggestive of a static conformation. In contrast, two-dimensional electron microscopy studies and three-dimensional reconstruction techniques have yielded different structures. These fundamental differences between EM and other ultrastructural studies have created a long standing quandary, which I have addressed and resolved using spectroscopic electron microscopy and statistical analyses of nucleosome images in a study of nucleosome structure with ionic environment.

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GENE ACTIVATION IN MAMMARY CELLS

Acta Endocrinologica ◽

10.1530/acta.0.071s346 ◽

1972 ◽

Vol 71 (2_Suppla) ◽

pp. S346-S368 ◽

Cited By ~ 4

Author(s):

Roger W. Turkington ◽

Nobuyuki Kadohama

Keyword(s):

Cell Differentiation ◽

Gene Transcription ◽

Hormonal Regulation ◽

Gene Activation ◽

Milk Proteins ◽

Mouse Mammary Gland ◽

Nuclear Proteins ◽

Mammary Cells ◽

Alveolar Cells ◽

Mammary Cell

ABSTRACT Hormonal activation of gene transcription has been studied in a model system, the mouse mammary gland in organ culture. Transcriptive activity is stimulated in mammary stem cells by insulin, and in mammary alveolar cells by prolactin and insulin. Studies on the template requirement for expression of the genes for milk proteins demonstrate that DNA methylation has an obligatory dependence upon DNA synthesis, but is otherwise independent from hormonal regulation of mammary cell differentiation. Incorporation of 5-bromo-2′deoxyuridine into DNA selectively inhibits expression of the genes for specific milk proteins. Undifferentiated mammary cells activate the synthesis of specific acidic nuclear proteins when stimulated by insulin. Several of these induced acidic nuclear proteins are undetectable in unstimulated undifferentiated cells, but appear to be characteristic components of the nuclei of differentiated cells. These results indicate that mammary cell differentiation is associated with a change in acidic nuclear proteins, and they provide evidence to support the concept that acidic nuclear proteins may be involved in the regulation of gene transcription and of mammary cell differentiation.

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