506 / 2019-03-01 00:18:19

A role for the nuclear pore in nucleocytoplasmic partitioning and the maintenance of temperature compensation of the circadian clock

Circadian clock, temperature compensation, TOC1, NUA

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Nucleocytoplasmic shuttling is essential for proper clock function although few components of the nuclear pore (NP) have been implicated as regulatory in any circadian system (1, 2). We have identified mutations in NP components in Arabidopsis that lengthen circadian period and are associated with mRNA export defects and misregulated protein sumoylation. NUCLEAR PORE ANCHOR (NUA), with similarity to the inner nuclear basket proteins Tpr (Translocated Promoter Region), Mlp1/Mlp2 (Myosin-like proteins 1 and 2), and Megator is located at the inner nuclear envelope within the “nuclear basket” of the NP.

We find circadian period is lengthened in nua mutants by 1-2 hours, but the severity of the defect is strongly influenced by ambient temperature, resulting in a marked loss of temperature compensation.

Analysis of mRNA and protein levels of known clock genes show only select and limited effects on mRNA and protein levels. Strikingly, double mutants between nua and select clock mutants point to TOC1 as a key element affected by NUA loss. The short period toc1 mutant (21 hrs) is fully epistatic to the long period of the nua mutant at all temperatures tested. Data will be presented to suggest that one role for NUA in the circadian system is in the regulation of the nucleocytoplasmic partitioning of select (TOC1 and possibly others) clock proteins.