How chromosomal translocations arise to cause cancer: Gene proximity, trans-splicing, and DNA end joining.

Chromosomal translocations (CTs) are a genetic hallmark of cancer. They could be identified as recurrent genetic aberrations in hemato-malignancies and solid tumors. More than 40% of all "cancer genes" were identified in recurrent CTs. Most of these CTs result in the production of oncofusion proteins of which many have been studied over the past decades. They influence signaling pathways and/or alter gene expression. However, a precise mechanism for how these CTs arise and occur in a nearly identical fashion in individuals remains to be elucidated. Here, we performed experiments that explain the onset of CTs: (1) proximity of genes able to produce prematurely terminated transcripts, which lead to the production of (2) trans-spliced fusion RNAs, and finally, the induction of (3) DNA double-strand breaks which are subsequently repaired via EJ repair pathways. Under these conditions, balanced chromosomal translocations could be specifically induced. The implications of these findings will be discussed.

Vaccine-induced COVID-19 mimicry syndrome.

To fight the COVID-19 pandemic caused by the RNA virus SARS-CoV-2, a global vaccination campaign is in progress to achieve the immunization of billions of people mainly with adenoviral vector- or mRNA-based vaccines, all of which encode the SARS-CoV-2 Spike protein. In some rare cases, cerebral venous sinus thromboses (CVST) have been reported as a severe side effect occurring 4-14 days after the first vaccination and were often accompanied by thrombocytopenia. Besides CVST, splanchnic vein thromboses (SVT) and other thromboembolic events have been observed. These events only occurred following vaccination with adenoviral vector-based vaccines but not following vaccination with mRNA-based vaccines. Meanwhile, scientists have proposed an immune-based pathomechanism and the condition has been coined vaccine-induced immune thrombotic thrombocytopenia (VITT). Here, we describe an unexpected mechanism that could explain thromboembolic events occurring with DNA-based but not with RNA-based vaccines. We show that DNA-encoded mRNA coding for Spike protein can be spliced in a way that the transmembrane anchor of Spike is lost, so that nearly full-length Spike is secreted from cells. Secreted Spike variants could potentially initiate severe side effects when binding to cells via the ACE2 receptor. Avoiding such splicing events should become part of a rational vaccine design to increase safety of prospective vaccines.