Chasing Particularities of Guanine- and Cytosine-Rich DNA Strands

By substitution of natural nucleotides by their abasic analogs (i.e., 1',2'-dideoxyribose phosphate residue) at critically chosen positions within 27-bp DNA constructs originating from the first intron of N-myc gene, we hindered hybridization within the guanine- and cytosine-rich central region and followed formation of non-canonical structures. The impeded hybridization between the complementary strands leads to time-dependent structural transformations of guanine-rich strand that are herein characterized with the use of solution-state NMR, CD spectroscopy, and native polyacrylamide gel electrophoresis. Moreover, the DNA structural changes involve transformation of intra- into inter-molecular G-quadruplex structures that are thermodynamically favored. Intriguingly, the transition occurs in the presence of complementary cytosine-rich strands highlighting the inability of Watson-Crick base-pairing to preclude the transformation between G-quadruplex structures that occurs via intertwining mechanism and corroborates a role of G-quadruplex structures in DNA recombination processes.

Effect of ulnar tunnel location on elbow stability in double-strand lateral collateral ligament reconstruction

BACKGROUND

Double-strand lateral ulnar collateral ligament (LUCL) reconstruction is an effective treatment for posterolateral rotatory instability (PLRI) of the elbow, but anatomic landmarks for ulnar tunnel placement are often difficult to identify intraoperatively, which potentially can result in a nonanatomic LUCL reconstruction. This study investigated the effect of ulnar tunnel location on joint stability in double-strand LUCL reconstruction.

METHODS

PLRI was artificially created in 7 cadaveric elbows, and double-strand LUCL reconstruction was performed. Five different ulnar tunnels were made along the length of the ulna. In each specimen, each possible pair of 2 tunnels (10 total) were used for graft passage. Varus and posterolateral joint gapping was measured after joint loading using a 3-dimensional digitizer system and X-ray image intensifier.

RESULTS

No significant gapping was observed at the posterolateral ulnohumeral joint regardless of the location of the ulnar tunnels (P > .05). In contrast, the lateral radiocapitellar joint showed statistically significant varus gapping when both ulnar tunnels were placed proximal to the radial head-neck junction (P < .05).

DISCUSSION

This findings of study suggest that the location of the ulnar tunnels may not be as critical as that of the humeral tunnel during double-strand LUCL reconstruction and that posterolateral rotatory elbow stability can be achieved reasonably well as long as at least 1 of the 2 ulnar tunnels is located at or distal to the radial head-neck junction level.

How life changes itself: the Read-Write (RW) genome

The genome has traditionally been treated as a Read-Only Memory (ROM) subject to change by copying errors and accidents. In this review, I propose that we need to change that perspective and understand the genome as an intricately formatted Read-Write (RW) data storage system constantly subject to cellular modifications and inscriptions. Cells operate under changing conditions and are continually modifying themselves by genome inscriptions. These inscriptions occur over three distinct time-scales (cell reproduction, multicellular development and evolutionary change) and involve a variety of different processes at each time scale (forming nucleoprotein complexes, epigenetic formatting and changes in DNA sequence structure). Research dating back to the 1930s has shown that genetic change is the result of cell-mediated processes, not simply accidents or damage to the DNA. This cell-active view of genome change applies to all scales of DNA sequence variation, from point mutations to large-scale genome rearrangements and whole genome duplications (WGDs). This conceptual change to active cell inscriptions controlling RW genome functions has profound implications for all areas of the life sciences.