engleski

A novel role of Arabidopsis BPM1 protein in RNA- directed DNA methylation

Arabidopsis thaliana BPM1 protein belongs to six-membered MATH-BTB protein family. The best- known function of MATH-BTB proteins is their role as substrate-specific adaptors of cullin3- based E3 ligases in the ubiquitin-proteasome pathway. BTB domain enables assembly with the cullin while less conserved MATH domain serves as an adaptor and binds substrates destined for degradation via 26S proteasome. Targets of BPM1 include several transcription factors such as WRI1, HB6, DREB2A and MYB6. Through mediation of degradation of these transcription factors BPM1 is involved in the regulation of various plant processes including fatty acid metabolism, abscisic acid signalling regulation, flowering etc. Earlier results showed that BPM1 predominantly localizes in nucleus indicating cullin independent function of BPM1. Co-immunoprecipitation and mass spectrometry revealed interaction of BPM1 with DMS3 and RDM1, key components of RNA-directed DNA methylation (RdDM). However, exact role of BPM1 interaction with DMS3 and RDM1 and possible implications for RdDM pathway remain unknown. To furthermore elucidate putative role of BPM1 protein in RdDM yeast two hybrid and pull down assays were used to confirm direct interactions of BPM1 with DMS3 and RDM1. Additionally, role of MATH and BTB domain in the interaction with DMS3 and RDM1 was tested using truncated version of BPM1 protein with a single domain deletion. The results showed that BTB domain had higher affinity for interaction with RDM1, while both MATH and BTB domains appear to be equally important for interaction with DMS3. In addition, co-localization assay showed overlap of BPM1 and RdDM components while overexpression of BPM1 revealed change in DNA methylation pattern. These results indicate a novel role of BPM1 protein in RNA-directed DNA methylation pathway. Our next aim is to use ChIP in order to identify DNA sites where transcription or RdDM methylation could be influenced by BPM1 protein.

BPM1, RdDM, methylation

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