The first thing that comes into my mind is: you could connect to CICS via MQ and have an IS in the middle which would get messages from MQ and put them into UM. This might be a much oversized solution. But if you already have all the named components the solution could be easily implemented.
UM by itself does not send or receive anything. There must be some piece of active software that does this. It can be an IS but it also can be a custom Java program. CICS can be integrated in many ways as well. Without further details I can’t add anything.