Meng-Hsuan Han, Saiprasad Goud, Liang Song, and Nina Fedoroff *

Biology Department and Huck Institutes of Life Sciences, Pennsylvania State University, University Park, PA 16802

*To whom correspondence should be addressed.
E-mail:   nvf1@psu.edu

The Arabidopsis HYL1 gene encodes a nuclear double-stranded RNA-binding protein. A knockout mutation of the hyl1 gene is recessive and pleiotropic, causing developmental abnormalities, increasing sensitivity to abscisic acid, and reducing sensitivity to auxin and cytokinin. We report that levels of several microRNAs (miRNAs; miR159, -167, and -171) are reduced in homozygous mutant plants, and levels of two of three tested target mRNAs are elevated. Conversely, the miRNA levels are elevated in plants expressing a HYL1 cDNA from a strong promoter, and the corresponding target RNAs are reduced. These changes result from alterations in the stability of the target RNAs. However, double-stranded RNA-induced posttranscriptional gene silencing is unaffected by the hyl1 mutation. One-third to one-half of the cellular HYL1 protein is in a macromolecular complex, and a GFP-HYL1 fusion protein is found predominantly in the nucleus, although it is observed in both nucleus and cytoplasm in some cells. Within nuclei, HYL1 is associated with subnuclear
bodies and ring-like structures. These observations provide evidence that the HYL1 protein is part of a nuclear
macromolecular complex that is involved in miRNA-mediated gene regulation. Because hyl1 mutants show marked abnormalities in hormone responses, these results further suggest that miRNA-mediated changes in mRNA stability play a vital role in plant hormone signaling.

1. Persengiev SP, Zhu X, and Green MR, "Nonspecific, concentration-dependent stimulation and repression of mammalian gene expression by small interfering RNAs (siRNAs)".

2. Lai EC, Wiel C,  and Rubin GM, "Complementary miRNA pairs suggest a regulatory role for miRNA:miRNA duplexes".

3. Lai E, "RNA Sensors and Riboswitches: Self-Regulating Messages".

4. Frenster JH, "Nuclear Ribosomes and RNA-RNA Duplexes".

5. Kronenberg LH,  and Humphreys T, "Double-Stranded Ribonucleic Acid in Sea Urchin Embryos".

Topics in:  Euchromatin,  active DNA, and  RNA  ribo-regulators:

Reviews and Research:

Links to Euchromatin Activator RNA Reviews:
Links to Euchromatin Activator RNA Research:
Links to RNA as a Therapeutic Agent:
Links to Hodgkin Lymphoma Immuno-Pathology:
Links to Activated T-Lymphocyte Immunotherapy:
Links to Medical Systems Biology:

"Ultrastructural Probes of Active DNA Sites, and the RNA Activators of DNA".
 

For Further Information and Feedback:
E-mail: frenster@euchromatin.net