What are two main types of posttranscriptional modifications that take place in the mrna of eukaryotes?

Addition of poly A tail and and addition of 5' cap

Explanation:

In eukaryotes, many post-transcriptional modification takes place like 5' capping, polyadenylation, and splicing. In 5' capping 7-methyl guanosine is added toward the 5' end of mRNA by the action of a enzyme called guanyl transferase. This cap protects mRNA from degradation.

In polyadenylation up to 250 adenosine nucleotides are added at the 3' end of the mRNA and it is called poly-A tail. Poly A polymerase is the enzyme that is responsible for polyadenylation.

Therefore two main post transcription modifications are 5' capping and polyadenylation.