Intronic Signaling Pathway System (ISPS): Extended Scientific Documentation

Intronic Signaling Pathway System (ISPS) Extended Scientific Documentation Introduction The Intronic Signaling Pathway System (ISPS) is a novel theoretical framework proposing that excised introns, rather than being inert by-products of RNA splicing, retain regulatory functions through transient interactions with transcription factors (TFs). This mechanism may modulate gene expression dynamics by sequestering TFs in the nucleoplasm through structured RNA lariats, contributing to negative feedback loops independent of classical DNA→TF regulation. Methods We analyzed intronic sequences from pro-inflammatory genes including TNF, IL6, and IL1B. For each intron, we performed: 1. Extraction of genomic sequences from UCSC Genome Browser (hg38), preserving correct strand orientation. 2. Branch Point (BP) identification using the YNYURAY consensus motif and trimming 3′ intronic tails. 3. Motif scanning using FIMO (MEME Suite) with a permissive threshold (p-value = 0.1) appropriate for intronic TFBS. 4. Structural folding using RNAfold (ViennaRNA package). 5. Visualization of secondary structures using Forna. 6. Mapping of TFBS coordinates onto RNA structural domains to determine accessibility (loops, bulges, multiloops, stems). Preliminary Results We identified extensive clustering of NFκB1 and STAT-binding motifs within introns of IL1B and IL6. TFBS clusters were consistently enriched within accessible structural regions such as loops and multiloops. These findings support the ISPS hypothesis that introns act as dynamic TF sequestration platforms. Cluster Region (nt) TFBS Count Accessibility 1 5–82 6 Highly accessible loops 2 158–201 8 Large loop region 3 206–260 5 Semi-flexible arm 4 280–343 10 Megacluster – multiloop 5 350–423 17 Megacluster – largest region 6 429–498 4 Distal loops Representative RNA Structures and TFBS Mapping Below are included key structural visualizations from Forna for IL1B introns 1 and 2, highlighting the spatial organization of TFBS clusters relative to RNA loops and stems. Extended Hypothesis We propose that intronic RNA lariats act as transient regulatory hubs capable of modulating the availability of transcription factors (TFs), particularly under inflammatory conditions. This mechanism may explain: • Rapid attenuation of NFκB1-driven transcription. • Oscillatory activation patterns observed in cytokine genes. • Differences in feedback regulation between intron-rich and intron-poor genes. We hypothesize that ISPS constitutes an evolutionarily conserved regulatory layer integrating RNA structure, transcription factor dynamics, and inflammatory gene expression. References 1. MEME Suite: Multiple EM for Motif Elicitation. 2. ViennaRNA Package: RNA Secondary Structure Prediction. 3. UCSC Genome Browser: Kent et al. 4. NFκB Signaling Pathway Reviews (Nature Reviews Immunology). 5. Splicing and RNA Lariat Dynamics (RNA Journal).