title: Dynamics of miRNA driven feed-forward loop depends upon miRNA action mechanisms.
abstract: BACKGROUND
  We perform the theoretical analysis of a gene network sub-system, composed of a feed-forward loop, in which the upstream transcription factor regulates the target gene via two parallel pathways: directly, and via interaction with miRNA.
  
  
  RESULTS
  As the molecular mechanisms of miRNA action are not clear so far, we elaborate three mathematical models, in which miRNA either represses translation of its target or promotes target mRNA degradation, or is not re-used, but degrades along with target mRNA. We examine the feed-forward loop dynamics quantitatively at the whole time interval of cell cycle. We rigorously proof the uniqueness of solutions to the models and obtain the exact solutions in one of them analytically.
  
  
  CONCLUSIONS
  We have shown that different mechanisms of miRNA action lead to a variety of types of dynamical behavior of feed-forward loops. In particular, we found that the ability of feed-forward loop to dampen fluctuations introduced by transcription factor is the model and parameter dependent feature. We also discuss how our results could help a biologist to infer the mechanism of miRNA action.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Duk
authors.forename: Maria G
authors.initials: MG
authors.lastname: Samsonova
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Samsonov
mesh_terms: D005786:Gene Expression Regulation; D053263:Gene Regulatory Networks; D035683:MicroRNAs / Q000378:metabolism*; D008957:Models, Genetic; D014176:Protein Biosynthesis; D020871:RNA Stability; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D035683:MicroRNAs; D014157:Transcription Factors