At the next stage, RNA molecules began to synthesize proteins, first by developing RNA adaptor molecules that can bind activated amino acids and then by arranging them according to an RNA template using other RNA molecules such as the RNA core of the ribosome.
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Rose, George D.
The Piwi-interacting RNAs, which associate
with proteins called piwi proteins which help regulate splicing, especially in spermatogenesis (sperm cell production).
In contrast, according to recent data, there is a strong evidence that anucleate platelets contain a functional spliceosome , mRNAs , rRNA, rough endoplasmic reticulum and polyribosomes, as well as numerous translation factors including 3'-UTR RNA- and poly(A)-binding protein . It is therefore believed that platelets maintain functionally intact protein translational capabilities accompanied by posttranslational modifications . Recently we were able to detect RNA in washed human RBCs . In this study we used microarray technique to identify genes possibly present and translated in human RBCs.
Human erythrocyte lack a nucleus and are thought to be void of protein synthesis. In contrast, we have found that total RNA from human RBCs resembles typical eukaryotic RNA with 5S-80S sedimentation distributions, and contains standard 28S- and18S-rRNA bands (Fig. ). Total RNA from nucleated avian erythrocytes was discovered to have from 5 to 60 S sedimentation rates . Identification of each unique RNA-class within the RNA pool as well as genetic mechanisms from both nucleated and anucleate erythrocytes awaits future studies.
For the first time we report about the presence of genes in human RBCs encoding initiation, activation and regulation of transcription and translation (for instance RNA polymerises I,II,III, zinc/PHD finger- DNA-binding proteins, cysteinyl, lysyl-tRNA synthetase), important RNA-stabilising factor - poly(A) binding protein, anti-apoptotic proteins (for instance beclin 1, reticulon 4, BCL2, IAP) together with genes for RNA degradation (for example ribonuclease T2) as well as genes encoding typical apoptotic proteins such as cyclooxygenase, apoptotic protease activating factor, caspase 8. Other authors were able to show a protein synthesis in human platelets by megakaryocyte-derived mRNAs . The finding of RNA in anucleate cells like erythrocytes support the idea of nucleus independent protein synthesis and supports data about possible mechanism of globin m-RNA stability in human RBCs.