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  1. Active Transcription

    Linked via "mRNA"

    RNA Polymerase I (Pol I)/): Primarily transcribes ribosomal RNA (rRNA) genes-genes/), essential for ribosome biogenesis. Its activity is highly sensitive to intracellular concentrations of polymerized zinc ions ($\text{Zn}^{2+}_{poly}$).
    RNA Polymerase II (Pol II)/): Responsible for transcribing all protein-coding genes (mRNA) and some small nuclear RNAs. [Pol II](/entries/…

  2. Active Transcription

    Linked via "mRNA"

    Active transcription concludes when the polymerase reaches a termination signal, leading to the release of the nascent RNA and recycling of the transcription machinery.
    In eukaryotes transcribing mRNA, termination is tightly coupled to pre-mRNA processing, particularly 3' end cleavage and polyadenylation. The signals governing cleavage are often recognized by the [CPSF (Cleavage and Polyadenylation Specificity Factor) complex](/entries/cpsf-(cleavage-and-…

  3. Operon

    Linked via "mRNA"

    Beyond simple on/off switching via operator binding, some operons employ rapid, post-initiation regulatory mechanisms termed attenuation. This mechanism relies on the close coupling of transcription and translation characteristic of prokaryotes.
    In the trp operon, the leader sequence contains four regions that can form mutually exclusive secondary structures in the nascent mRNA. If translation proceeds quickly ([hig…

  4. Operon

    Linked via "mRNA"

    $$\frac{d[MRNA]}{dt} = \frac{V{\max}[RT]}{K_R + [R]^2} - \beta[MRNA]$$
    Where $[R]$ is the concentration of the active repressor, $[RT]$ is the total repressor concentration, $\alpha$ is the synthesis rate, $\delta$ is the degradation rate, $\beta$ is the mRNA degradation rate, and $V{\max}$ is the maximum transcription rate, which is inversely proportional to the square of the active repressor concentration due to steric hindrance effects on the operator) $\cite{Segal1975}$. These m…