High impact information on HEN1

• HEN1 may achieve these functions by regulating the expression of AG. hen1 single mutants exhibit pleiotropic phenotypes such as reduced organ size, altered rosette leaf shape and increased number of coflorescences, during most stages of development [1].
• Therefore, HEN1, like the A function gene AP2, plays multiple roles in plant development as well as acting in organ identity specification in the flower [1].
• In addition to a Dicer homolog, DCL1, the biogenesis of miRNAs in Arabidopsis requires another protein, HEN1. miRNAs are reduced in abundance and increased in size in hen1 mutants [2].
• We found that HEN1 is a miRNA methyltransferase that adds a methyl group to the 3'-most nucleotide of miRNAs, but the role of miRNA methylation was unknown [2].
• Here, we show that siRNAs from sense transgenes, hairpin transgenes, and transposons or repeat sequences, as well as a new class of siRNAs known as trans-acting siRNAs, are also methylated in vivo by HEN1 [2].

Biological context of HEN1

• Arabidopsis HEN1: a genetic link between endogenous miRNA controlling development and siRNA controlling transgene silencing and virus resistance [3].
• While the four DCLs are partially redundant for CaLCuV-induced mRNA degradation, DCL4 in conjunction with RDR6 and HEN1 specifically facilitates extensive virus-induced silencing in new growth [4].
• In Arabidopsis, point mutations in or short truncations of the nuclear DICER-LIKE1 (DCL1) or HEN1 protein reduce miRNA accumulation and increase uncleaved target mRNAs accumulation, resulting in developmental abnormalities [5].
• The fold-recognition approach was used to identify related methyltransferases with experimentally solved structures and to guide the homology modeling of the HEN1 catalytic domain [6].
• Elevated levels of DCL1 RNAs were also detected in miRNA-defective hen1 mutant plants and in plants expressing a virus-encoded suppressor of RNA silencing (P1/HC-Pro), which inhibits miRNA-guided degradation of target mRNAs [7].

Associations of HEN1 with chemical compounds

• However, the biogenesis of plant miRNAs consists of an additional step, i.e., the miRNAs are methylated on the ribose of the last nucleotide by the miRNA methyltransferase HEN1 [8].

Other interactions of HEN1

• Additionally, we show that CaMV infection impairs processing of endogenous RDR6-derived double-stranded RNA, while ORMV prevents HEN1-mediated methylation of small RNA duplexes, suggesting two novel viral strategies of silencing suppression [4].
• We showed that HEN1, like the C function gene AGAMOUS, acts to specify reproductive organ identities and to repress A function [1].
• These results suggest that CRM2 and ER may act in different ways to generate wild-type inflorescence [9].

Analytical, diagnostic and therapeutic context of HEN1

• Based on the multiple sequence alignment a phylogenetic tree of the HEN1 family was constructed [6].

References