| Kinetics of Incorporation of Uridine-C into L Cell RNA Biophysical Journal, Volume 4, Issue 4, 1 July 1964, Pages 267-284 A.V. Rake and A.F. Graham Abstract Five components have been isolated from L cells by a combination of phenol extraction procedures and sedimentation analysis through sucrose gradients. These components are identified by their sedimentation rates. The 50S and 40S components are derived from the nucleus, the 32S and 18S from ribosomal RNA, and the 4S fraction is the soluble RNA of the cell. L cells were supplied with uridine-C under steady-state conditions and the rate of uptake of C into each component was measured. Analysis of the results suggests that the delay in entry of C into ribosomal RNA is occasioned by two sequential precursors and that 50S and 40S RNA meet the kinetic requirements for these precursors. 4S RNA seems to contain two components that label at different rates. Abstract | PDF (1549 kb) |
| Sedimentation Analysis of DNA from Irradiated and Unirradiated L Cells Biophysical Journal, Volume 12, Issue 4, 1 April 1972, Pages 369-383 M.W. McBurney, F.L. Graham and G.F. Whitmore Abstract DNA, released from unirradiated mouse L-cells gently lysed in a thin layer of 2% sucrose on top of an alkaline sucrose gradient, was found to sediment in a narrow band with a sedimentation coefficient of about 500S. Exposure of cells to increasing doses of X-rays (89–712 rads) continuously reduced the DNA sedimentation velocity until, after about 890 rads, the DNA appeared in a narrow peak with a sedimentation coefficient of approximately 180S. As the dose given to cells was increased beyond 890 rads, the sedimentation coefficient of the DNA released continued to decrease and the sedimentation profiles now broadened in a manner consistent with the random production of single-strand breaks in the DNA. The DNA released from unirradiated cells (500S) is thought to be loosely aggregated and only partially single stranded. It is presumed that cells exposed to low doses of radiation release DNA with marked reductions in sedimentation coefficient because single-strand breaks produced in the DNA aid the alkaline denaturation process. By using the system to be described, it has been possible to demonstrate DNA repair (rejoining of X-ray-induced single-strand breaks) during postirradiation incubation of cells given doses as low as 400 rads. Abstract | PDF (843 kb) |
| The C-Terminal SH3 Domain of CRKL as a Dynamic Dimerization Module Transiently Exposing a Nuclear Export Signal Structure, Volume 14, Issue 12, 1 December 2006, Pages 1741-1753 Maria Harkiolaki, Robert J.C. Gilbert, E. Yvonne Jones and Stephan M. Feller Summary CRKL plays essential roles in cell signaling. It consists of an N-terminal SH2 domain followed by two SH3 domains. SH2 and SH3N bind to signaling proteins, but the function of the SH3C domain has remained largely enigmatic. We show here that the SH3C of CRKL forms homodimers in protein crystals and in solution. Evidence for dimer formation of full-length CRKL is also presented. In the SH3C dimer, a nuclear export signal (NES) is mostly buried under the domain surface. The same is true for a monomeric SH3C obtained under different crystallization conditions. Interestingly, partial SH3 unfolding, such as occurs upon dimer/monomer transition, produces a fully-accessible NES through translocation of a single β strand. Our results document the existence of an SH3 domain dimer formed through exchange of the first SH3 domain β strand and suggest that partial unfolding of the SH3C is important for the relay of information in vivo. Summary | Full Text | PDF (1806 kb) |
Copyright © 1962 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 2, Issue 5, 409-421, 1 September 1962
doi:10.1016/S0006-3495(62)86864-7
Articles
B.P. Sagik, M.H. Green, M. Hayashi and S. Spiegelman
Previous investigations suggested that the size of “informational” or “messenger” RNA was confined to sedimentation rates lying between 8 and 14S. These involved procedures permitting extended contact of the RNA with enzymatically active extracts. The present study re-examined the size distribution of T2-complementary RNA isolated by a method which minimized enzymatic degradation. A much greater diversity in size distribution (4S to 25S) was observed. Experiments are described indicating that 8 to 12S informational RNA does not readily attach to the 16S and 23S ribosomal components under the conditions used for sedimentation analysis.