Nascent RNA antagonizes the interaction of a set of regulatory proteins with chromatin.

A number of regulatory factors are recruited to chromatin by specialized RNAs. Whether RNA has a more general role in regulating the interaction of proteins with chromatin has not been determined. We used proteomics methods to measure the global impact of nascent RNA on chromatin in embryonic stem cells. Surprisingly, we found that nascent RNA primarily antagonized the interaction of chromatin modifiers and transcriptional regulators with chromatin. Transcriptional inhibition and RNA degradation induced recruitment of a set of transcriptional regulators, chromatin modifiers, nucleosome remodelers, and regulators of higher-order structure. RNA directly bound to factors, including BAF, NuRD, EHMT1, and INO80 and inhibited their interaction with nucleosomes. The transcriptional elongation factor P-TEFb directly bound pre-mRNA, and its recruitment to chromatin upon Pol II inhibition was regulated by the 7SK ribonucleoprotein complex. We postulate that by antagonizing the interaction of regulatory proteins with chromatin, nascent RNA links transcriptional output with chromatin composition

Carbon Dioxide Adsorption-Induced Deformation of Microporous Carbons

Applying the thermodynamic model of adsorption-induced deformation of microporous carbons developed recently (Kowalczyk, P.; Ciach, A.; Neimark, A. Langmuir 2008, 24, 6603), we study the deformation of carbonaceous amorphous porous materials due to adsorption of carbon dioxide at 333 K and pressures up to 27 MPa. The internal adsorption stress induced by adsorbed/compressed carbon dioxide is very high in the smallest ultramicropores (for instance, solvation pressure in 0.23 nm ultramicropore reaches 3.2 GPa at 27 MPa). Model calculations show that any sample of carbonaceous porous solid containing a fraction of the smallest ultramicropores with pore size below 0.31 nm will expand at studied operating conditions. This is because the high internal adsorption stress in ultramicropores dominates sample deformation upon adsorption of carbon dioxide at studied operation conditions. Interestingly, the nonmonotonic deformation (i.e., initial contraction and further expansion) of the above mentioned porous materials upon adsorption of carbon dioxide at 333 K is also theoretically predicted. Our calculations reproduce quantitatively the strain isotherm of carbon dioxide on carbide-derived activated carbon at 333 K and experimental pressures up to 2.9 MPa. Moreover, we extrapolate adsorption and strain isotherms measured by the gravimetric/dilatometric method up to 27 MPa to mimic geosequestration operating conditions. And so, we predict that expansion of the studied carbon sample reaches 0.75% at 27 MPa and 333 K. Presented simulation results can be useful for the interpretation of the coal deformation upon sequestration of carbon dioxide at high pressures and temperatures