Structural elements of dynamic RNA strings

Area of Science:

• Molecular Biology
• RNA Biology
• Gene Expression

Background:

• Short transient secondary structures form during RNA transcription, serving as initial sites for protein binding.
• These structures are crucial for the proper folding and maturation of RNA molecules, including gene transcripts.

Purpose of the Study:

• To investigate the characteristics of transient secondary structures in different RNA transcripts.
• To compare the folding and compaction of the insulin gene transcript (IGT) and the 25-hydroxyvitamin D3 1-alpha-hydroxylase gene transcript (HDHGT).

Main Methods:

• Analysis of RNA chain length and stem-loop formation for IGT and HDHGT.
• Calculation of RNA chain shortening and contraction ratios during folding.
• Comparison of secondary structures in exons and introns between IGT and HDHGT.

Main Results:

• Both IGT (1,430 nucleotides) and HDHGT (4,825 nucleotides) form numerous stem-loops, with varying densities.
• No significant differences in transient secondary structures were observed between the exons of IGT and HDHGT, but significant differences were found in introns.
• Maximal RNA chain contraction ratios differed significantly between IGT and HDHGT, suggesting distinct final compaction degrees in different heterogeneous nuclear ribonucleoproteins (hnRNPs).

Conclusions:

• Initial RNA-protein (RNP) fibril formation may involve shared mechanisms, while final compaction can vary.
• Co-transcriptional folding is essential for RNA maturation processes like splicing, potentially guided by "chaperones" or "match makers".
• Exon regions exhibit snap-back complementarity aiding splice site joining, with minimal changes to exons post-splicing.