Protein-dependent conformational behavior of DNA in chromatin

Journal Article · Tue May 19 00:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00384a032· OSTI ID:5879505

Riehm, M R; Harrington, R E

Information from circular dichroism (CD) and DNA thermal denaturation has been used in concert to study the conformation behavior of DNA in the extended 11-nm fiber of chromatin isolated from HeLa nuclei. The histone-dependent conformational states of the system were investigated by selectively removing the hydrophilic histone domains with trypsin. These were compared to acetylated chromatin from the same source. The integrated intensity of the positive CD band for DNA above 260 nm is found to increase with the content of relatively unstressed B-form DNA. This same increase is observed along the series of whole, H1-stripped, and trypsinized chromatin samples as protein is removed. Hence, the ratio of percent hyperchromicity to integrated CD band intensity of the respective melting transitions provides useful information on the conformational state of DNA in the three principal regions of the chromatin fiber: the central loop and flanking nucleosomal regions and the linker. Results from this study suggest that central loop DNA in both hyperacetylated and control chromatin relaxes as protein is removed. However, hyperacetylated chromatin shows significantly less dependence than control chromatin upon core histone hydrophilic domains in the flanking and linker regions. Thus, histone hyperacetylation evidently relaxes DNA in chromatin with no major overall conformational changes. A possible role of histone hyperacetylation may therefore be to reduce cooperativity in the unfolding transition in chromatin and thus provide for greater localized control of unfolding during transcription.

• Research Organization: Univ. of Nevada, Reno
• OSTI ID: 5879505
• Journal Information: Biochemistry; (United States), Vol. 26:10
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CHROMATIN
MAGNETIC CIRCULAR DICHROISM
TEMPERATURE EFFECTS
DNA
CONFORMATIONAL CHANGES
ACETYLATION
ELECTROPHORESIS
HELA CELLS
MELTING POINTS
NUCLEIC ACID DENATURATION
TRANSCRIPTION
ACYLATION
CHEMICAL REACTIONS
DICHROISM
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
550200* - Biochemistry