The key difference between drosha and dicer is that drosha is a ribonuclease III enzyme that converts pri-microRNA to pre-microRNA while dicer is a ribonuclease III enzyme that converts pre-microRNA to mature microRNA.
MicroRNA is a small single-stranded non-coding RNA molecule containing about 22 nucleotides. It is found in plants, animals, and some viruses. It normally functions in RNA silencing and post-transcriptional regulation of gene expression. MicroRNA is synthesized as long RNA primary transcripts called pri-microRNA (primary microRNA). Later, it converts to mature microRNA. This event is called microRNA processing. Many enzymes are involved in microRNA processing. Drosha and dicer are two ribonuclease III enzymes involved in microRNA processing.
CONTENTS
1. Overview and Key Difference
2. What is Drosha
3. What is Dicer
4. Similarities – Drosha and Dicer
5. Drosha vs Dicer in Tabular Form
6. Summary – Drosha vs Dicer
What is Drosha?
Drosha is a class 2 ribonuclease III enzyme coded by the human gene DROSHA. It is usually a nuclease enzyme involved in the initial step of microRNA processing. Drosha enzyme can be found in the nucleus of the cell. Moreover, this enzyme works closely with DGCR8 in microRNA processing. Human drosha was cloned for the first time in 2000. The other enzymes involved in microRNA processing in correlation to this enzyme are dicer and argonaute. Both drosha and DGCR8 are localized in the cell nucleus, where pri-microRNA converts to pre-microRNA. Normally, microRNA molecule is synthesized as a long RNA transcript known as pri-microRNA, which is cleaved by the drosha enzyme to produce a characteristic stem-loop structure called pre-microRNA (70 base pairs).
Figure 01: Drosha
Drosha enzyme exists as a part of a protein complex called the microprocessor complex. This complex also contains DGCR8 protein. This DGCR8 protein is essential for drosha activity. Furthermore, drosha also participates in the DNA damage response. Drosha and other enzymes in microRNA processing are important in cancer prognosis. They are down-regulated in some types of breast cancer. The variant of drosha protein called c-drosha appears to be enriched in various types of breast cancer, colon cancer, esophageal cancer.
What is Dicer?
Dicer is a ribonuclease III enzyme that converts pre microRNA to mature microRNA. It is encoded by a human gene called DICER1. This enzyme is a member of the RNase III superfamily. It is also known as endoribonuclease dicer or helicase with RNase motif. Usually, dicer cleaves double-stranded RNA and pre-microRNA (precursor microRNA) into short double-stranded RNA fragments (small interfering RNA) and microRNA, respectively. A 2nt 3’ overhang generated in pre-microRNA by drosha is recognized by dicer in the cytoplasm. Dicer is also involved in the downstream processing events of microRNA processing. Later, pre-microRNA is processed by RNase dicer into mature microRNA in the cytoplasm of a cell.
Figure 02: Dicer
Similar to drosha, the dicer enzyme is also involved in DNA damage response. Furthermore, in the analysis of lung and ovarian cancer, poor prognosis and decreased patient survival times normally correlate with decreased dicer and dosha expression. Therefore, altered expression of dicer may lead to tumorigenesis.
What are the Similarities Between Drosha and Dicer?
- Drosha and dicer are two ribonuclease III enzymes involved in microRNA processing.
- Both are protein molecules made up of amino acids.
- These enzymes can cleave RNA molecules into fragments.
- They participate in the DNA damage response as well.
- The altered expression of drosha and dicer may lead to tumorigenesis.
- Certain microRNAs do not require drosha or dicer mediated cleavage.
What is the Difference Between Drosha and Dicer?
Drosha is a ribonuclease III enzyme that converts pri-microRNA to pre-microRNA while dicer is a ribonuclease III enzyme that converts pre-microRNA to mature microRNA. Thus, this is the key difference between drosha and dicer. Furthermore, drosha is a ribonuclease enzyme present in the nucleus of the cell, while dicer is a ribonuclease enzyme that is present in the cytoplasm of the cell.
The below infographic presents the differences between drosha and dicer in tabular form for side by side comparison.
Summary – Drosha vs Dicer
MicroRNA processing is an event that takes place in the cell where certain enzymes convert primary microRNA to mature microRNA. Drosha and dicer are two ribonuclease III enzymes involved in microRNA processing. Drosha enzyme converts pri-microRNA to pre-microRNA while dicer enzyme converts pre-microRNA to mature microRNA. So, this is the summary of the difference between drosha and dicer.
Reference:
1. “Drosha.” An Overview | ScienceDirect Topics.
2. “Dicer.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “MiRNA-biogenesis” By Narayanese at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “MiRNA processing” By User:Narayanese (Wikipedia Inglés) – Wikipedia Inglés: creada por un usuario, en base a illustration in Esquela-Kerscher A, Slack FJ (2006). “Oncomirs — microRNAs with a role in cancer” Nature Reviews Cancer 6: 259–69. DOI:10.1038/nrc1840. (CC BY-SA 3.0) via Commons Wikimedia