Um. Look at your code:
Session["announcementData"] = announcementData;
if ((NewsDataList)Session["newsApiResponse"] != null)
{
newsData = (NewsDataList)Session["newsApiResponse"];
If you use different keys, you get different data...
Try:
if ((NewsDataList)Session["announcementData"] != null)
{
newsData = (NewsDataList)Session["announcementData"];