Posttranslationally modified ornithine decarboxylase may regulate RNA polymerase I activity

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Ornithine decarboxylase (ODC) plays a role in polyamine metabolism.
• Transglutaminase (TGase) catalyzes the formation of cross-links between proteins.
• RNA polymerase I is crucial for ribosomal RNA synthesis.

Purpose of the Study:

• To investigate the effect of ODC transamidated with putrescine on RNA polymerase I activity.
• To determine the mechanism of ODC-putrescine conjugate action on RNA polymerase I.
• To identify the potential role of ODC-putrescine conjugate as a subunit of RNA polymerase I.

Main Methods:

• Purification of ornithine decarboxylase (ODC) and transglutaminase (TGase).
• Incubation of purified ODC-putrescine conjugate with isolated rat liver nuclei.
• Measurement of RNA polymerase I activity by UMP incorporation.

Main Results:

• ODC transamidated with putrescine stoichiometrically increased RNA polymerase I activity.
• The ODC-putrescine conjugate was not reused but degraded after each initiation.
• Consistent stimulation of UMP incorporation was observed with ODC-putrescine conjugate addition.

Conclusions:

• ODC transamidated by its product putrescine may be a labile subunit of RNA polymerase I.
• This post-translational modification of ODC influences RNA polymerase I activity.
• The findings suggest a novel regulatory mechanism for rRNA synthesis.