The APT complex is involved in non-coding RNA transcription and is distinct from CPF.

The 3'-ends of eukaryotic pre-mRNAs are processed in the nucleus by a large multiprotein complex, the cleavage and polyadenylation factor (CPF). CPF cleaves RNA, adds a poly(A) tail and signals transcription termination. CPF harbors four enzymatic activities essential for these processes, but how these are coordinated remains poorly understood.

Architecture of eukaryotic mRNA 3'-end processing machinery.

Newly transcribed eukaryotic precursor messenger RNAs (pre-mRNAs) are processed at their 3' ends by the ~1-megadalton multiprotein cleavage and polyadenylation factor (CPF). CPF cleaves pre-mRNAs, adds a polyadenylate tail, and triggers transcription termination, but it is unclear how its various enzymes are coordinated and assembled. Here, we show that the nuclease, polymerase, and phosphatase activities of yeast CPF are organized into three modules.

RNA polymerase II termination involves C-terminal-domain tyrosine dephosphorylation by CPF subunit Glc7.

At the 3' ends of protein-coding genes, RNA polymerase (Pol) II is dephosphorylated at tyrosine residues (Tyr1) of its C-terminal domain (CTD). In addition, the associated cleavage-and-polyadenylation factor (CPF) cleaves the transcript and adds a poly(a) tail. Whether these events are coordinated and how they lead to transcription termination remains poorly understood.

Change in heat capacity for enzyme catalysis determines temperature dependence of enzyme catalyzed rates.

The increase in enzymatic rates with temperature up to an optimum temperature (Topt) is widely attributed to classical Arrhenius behavior, with the decrease in enzymatic rates above Topt ascribed to protein denaturation and/or aggregation. This account persists despite many investigators noting that denaturation is insufficient to explain the decline in enzymatic rates above Topt. Here we show that it is the change in heat capacity associated with enzyme catalysis (ΔC(‡)p) and its effect on the temperature dependence of ΔG(‡) that determines the temperature dependence of enzyme activity.

The crystal structure of the intact E. coli RelBE toxin-antitoxin complex provides the structural basis for conditional cooperativity.

The bacterial relBE locus encodes a toxin-antitoxin complex in which the toxin, RelE, is capable of cleaving mRNA in the ribosomal A site cotranslationally. The antitoxin, RelB, both binds and inhibits RelE, and regulates transcription through operator binding and conditional cooperativity controlled by RelE. Here, we present the crystal structure of the intact Escherichia coli RelB2E2 complex at 2.