mRNA imprinting: Additional level in the regulation of gene expression

Abstract

Following its synthesis in the nucleus, mRNA undergoes various stages that are critical for the proper synthesis, localization and possibly functionality of its encoded protein. Recently, we have shown that two RNA polymerase II (Pol II) subunits, Rpb4p and Rpb7p, associate with the nascent transcript co-transcriptionally. This "mRNA imprinting" lasts throughout the mRNA lifetime and is required for proper regulation of all major stages that the mRNA undergoes. Other possible cases of co-transcriptional imprinting are discussed. Since mRNAs can be transported from the synthesizing cell to other cells, we propose that mRNA imprinting can also affect the phenotype of the recipient cells. This can be viewed as "mRNA-based epigenetics."

Figure 1

Model for a possible impact of mRNA imprinting on epigentics. Imprinted mRNA can be transported between cells via one of the following ways: (A) Imprinted mRNA can be transferred from mother to daughter cell, thus affecting the phenotype during bud growth and shortly after the daughter cell separates. (B) Imprinted mRNA can be transferred between neighboring cells through specific gates, such as plasmodesmata in plant tissues. (C) Imprinted mRNA can be transferred between distant cells through vesicles, such as exosomes. We propose that, in all these cases, the nature of imprinting can regulate the mRNA transport process itself, as well as the mRNA localization and translatability within the recipient cell. In this way, mRNA imprinting might contribute to epigenetics.