A model explaining mRNA level fluctuations based on activity demands and RNA age
Fig 8
Models of biomolecular level fluctuations.
(A) A one-unit model of biomolecular level fluctuations in a cell. TB represents the total abundance of biomolecules at all biomolecular ages. TA represents total biomolecular activity at all biomolecular ages. DA represents the demands of biomolecular activity in the cell. DA is influenced by stimuli from intra- and extracellular environments, and the difference between TA and DA determines the trigger or cessation of biomolecule production. d0, d 1, d2, …, d n are degradation coefficients. α0, α1, α2, …, αn are activity coefficients. P0 represents the level of nascent biomolecules per time. (B) A two-unit model of level fluctuations of RNAs and proteins derived from a gene in a cell. TR is the total amount of RNA at all ages. TRA is the total RNA activity at all ages. DRA is the demands for RNA activity. TPro is the total amount of protein at all ages. TPA is the total protein activity at all ages. DPA is the demands for protein activity. DPA corresponds to the external and internal stimuli. The differences between TPA and DPA and that between TRA and DRA define the intensity of the production and/or the degradation of proteins and RNAs, respectively. dr0, dr1, dr2, …, drn are degradation coefficients of RNA. dp0, dp1, dr2, …, dpn are degradation coefficients of protein. αr0, αr1, αr2, …, αrn are the activity coefficients of RNA. αp0, αp1, αp2, …, αpn are the activity coefficients of the protein. Tr0 is the amount of nascent RNA per time. Tp0 is the amount of nascent protein per time.