Rotating my character's spine based on an enemy location

As the title says , i have a 2D shooter project where i want the character upper torso rotating based on the nearest enemy . Finding which enemy is nearest to my character isnt a problem . I am stuck on how can i rotate the spine only .
PS. Normaly during gameplay the character doesnt look up or down .Just straight . I want to rotate his spine based on a box collision in front of him.