Accurate thermodynamic parameters improve RNA structure predictions and thus accelerate understanding of RNA function and the identification of RNA drug binding sites. Many viral RNA structures, such as internal ribosome entry sites, have internal loops and bulges that are potential drug target sites. Current models used to predict internal loops are biased toward small, symmetric purine loops, and thus poorly predict asymmetric, pyrimidine-rich loops with >6 nucleotides (nt) that occur frequently in viral RNA. This article presents new thermodynamic data for 40 pyrimidine loops, many of which can form UU or protonated CC base pairs. Uracil and protonated cytosine base pairs stabilize asymmetric internal loops. Accurate prediction rules are presented that account for all thermodynamic measurements of RNA asymmetric internal loops. New loop initiation terms for loops with >6 nt are presented that do not follow previous assumptions that increasing asymmetry destabilizes loops. Since the last 2004 update, 126 new loops with asymmetry or sizes greater than 2 × 2 have been measured. These new measurements significantly deepen and diversify the thermodynamic database for RNA. These results will help better predict internal loops that are larger, pyrimidine-rich, and occur within viral structures such as internal ribosome entry sites.
This content will become publicly available on April 29, 2023
Dynamics of CTCF- and cohesin-mediated chromatin looping revealed by live-cell imaging
Super-resolution live-cell imaging of CTCF- and cohesin-mediated chromatin loops reveals that these loops are rare and dynamic.
- Award ID(s):
- 2036037
- Publication Date:
- NSF-PAR ID:
- 10379463
- Journal Name:
- Science
- Volume:
- 376
- Issue:
- 6592
- Page Range or eLocation-ID:
- 496 to 501
- ISSN:
- 0036-8075
- Sponsoring Org:
- National Science Foundation
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