Insider trading is all about information held by "insiders", not about who owns what. So it would depend on whether you know something material and nonpublic when you liquidate your position (e.g., you know the acquisition is going terribly and the acquiring company is going to write it off).

If you hold stock in company A, and your current company B acquires company A, that's not insider trading if you already owned the stock in company A before you had any information that company B was going to make that decision.

It is, however, a conflict of interest for you to be involved in company B's acquisition of company A (e.g. influencing company B to buy company A), and might even rise to the level of a breach of your fiduciary duty to company B.

I know a woman who was part of a M&A team. On her first day, she was told her days of owning individual stocks in the industry were over. She could only purchase aggregate funds. Although, I do wonder if the same rules apply to the VPs who actually have to sign off on the deals.