I don't kwow how Sitemesh works, but I solved problems like that by using interceptor:
create a class that extends : HandlerInterceptorAdapter
Override the method postHandle and populate the modelAndView Object like this :
modelAndView.addObject("newslist",myNewsList);
So you will have a variable $newslist injected into all your views.
Don't forget to declare bean in your mvc-congig.xml :
<bean id="newsListInterceptor" class="mypackage.NewsListInterceptor"/>
As the interceptor is executed for each request I also use ehcache to store the result and avoid during a select in database for each call.