Analysis of Platelets From Patients With Thrombocythemia for Reverse Transcriptase and Virus-Like Particles2

Abstract

A preliminary analysis of an RNA-directed DNA polymerase was made and a C-type virus-like particle was identified in platelets from 2 patients with the myeloproliferative disorder thrombocythemia (primary, essential, hemorrhagic, or idiopathic thrombocythemia). Platelet homogenates were centrifuged through a sucrose equilibrium density gradient. Both endogenous and exogenous DNA polymerase activity was found at a density of 1.19 g/ml. No activity was seen at comparable densities in control gradients. Electron micrographs of thin sections of these platelets revealed a particle with the morphologic characteristics of a C-type virus; however, the diameter of this particle was about 80 nm, slightly lower than that commonly found for C-type particles. Critical-point dried specimens, from the fractions of the sucrose gradient at which DNA polymerase activity was found, contained particles of the same size and morphology as those in the thin sections.

Quantitation of RNA‐dependent platelet DNA polymerase in patients with myeloproliferative disorders

“…We define this platelet polymerase as an RNA-dependent DNA polymerase, since it efficiently utilized platelet RNA to synthesize DNA in vitro. This polymerase is probably the same as the enzyme identified earlier in MPD patients, using more qualitative methodology (Brodsky et al, 1975(Brodsky et al, , 1977. The individuals examined in this communication include untreated patients with ET, MF and PV and intermittently treated CML patients.…”

“…metabolism of these macromolecules. In particular, elevated levels of DNA polymerases in platelets of MPD patients (Bhattacharyya et al, 1974;Brodsky et al, 1975;Tarrago-Litvak et al, 19 79) may reflect increased genetic activity of megakaryocytes. Investigation of these polymerases could eventually lead to a better understanding of the pathophysiology of the myeloproliferative disorders.…”

Platelets should be at the Frontline: HIV Researchers and Care Providers Needs a lot of Sticky Notes

“…Additional studies provide evidence that platelets synthesize biologically relevant proteins, which are regulated via gene expression programs at the translational level [3]. This process does not require a nucleus: platelets contain ribosomes, essential spliceosome factors, small nuclear RNAs, endogenous pre-mRNAs, and translational factors necessary for protein synthesis [3][4][5][6][7][8][9].…”

“…Beyond the classical methods, platelets have developed extranuclear mechanisms to process and efficiently translate mRNAs into proteins [3][4][5][6][7][8][9]. Specialized post-transcriptional and translational mechanisms are now considered part of the platelet's functional repertoire.…”

An alternative approach to medical genetics based on modern evolutionary biology. Part 4: HERVs in cancer

“…19 Subsequently, reverse transcriptase activity coupled with EM pictures of HERVs have been detected in platelets from patients with primary proliferative polycythaemia and essential thrombocythaemia, 20 HERV-K protein synthesis (gag gene) has been detected in megakaryocytes from stem cells cultured from the peripheral blood of patients with essential thrombocythaemia, 21 with packaging of the gag protein into HERV-K viruses budding from the cell membrane of the megakaryocytes. While this suggested that HERV-Ks might be implicated in the myeloproliferative disorders, no firm conclusions could be drawn as to whether the HERVs were causative or acting in a responsive role.…”